+ What's your opinion on Waterproof, Hog, and Hollis drysuits?
I don't have any personal experience with those brands.
+ Do drysuits have less buoyancy than wetsuits?
Too many variables to consider: composition of drysuit material, thickness/material composition of drysuit undergarment, etc.
You need to do a proper in-water weight check to determine your minimum weighting requirements for your chosen exposure suit configuration.
Most of my friends have needed more lead when transitioning from wetsuit to drysuit.
+ Could you still wear a drysuit in warmer conditions or would be too hot?
Depends on your temperature tolerance and the type of drysuit (shell vs. neoprene/crushed neoprene vs. hybrid). Shell drysuits offer very little inherent insulation. Varying the undergarment can enable the diver to wear the shell drysuit in a fairly wide range of water temps. I wear my shell drysuit year-round in water temps ranging from high 40s to mid 60s (°F). Since I bought my drysuit for local diving (San Diego) several years ago, I can count the number of my local wetsuit dives on one hand. For me, drysuit diving in our SoCal conditions is just more comfortable.
+ How much of your air supply does the suit usually take up on a dive?
Negligible. This is really a non-issue. Gas consumption has a lot to do with how comfortable/relaxed a diver is in the water. After you figure out how to use the drysuit properly (10-20 dives), you'll realize that staying warm underwater translates into being comfortable/relaxed. The limited amount of gas you use to offset drysuit squeeze contributes to buoyancy (much like adding air to your BCD) and helps you stay warm. On the rare occasion that I find myself doing a wetsuit dive, there's always a time during the dive when I get annoyed with how cold I get. This is followed by a noticeable increase in gas consumption, feeling somewhat uncomfortable, and cutting the dive short. With my drysuit + appropriate undergarment + drygloves, I can do my typical 80-90 minute local dives in water temps in the 50s very comfortably.
When I initially switched over to a drysuit, I found that my gas consumption improved significantly. YMMV.
+ Maintenance-wise, what kind of overhead am I looking at to keep the suit leak-free?
A new suit should remain service-free for at least 1-2 years. The manufacturer should cover the cost of any unexpected leaks in that time frame.
Seal replacement will probably be the most common service procedure. DUI has a nifty ziploc-style (ZipSeal) wrist/neck system that is user-replaceable. The Whites Fusion has the Si-Tech system which allows user-replacement of seals. Seal material can be neoprene (lasts hundreds of dives but more prone to leakage), latex (more water-tight but degrades more quickly -- replace seals once a year or once every few years), or silicone (very comfortable, more expensive; newest on the market so not sure how well they hold up over time, probably longer than latex). Figure out which kind of seal you want and then we can talk about the cost to replace them. User-replaceable seals re generally the way to go. Prices vary considerably.
The most expensive part to repair on the drysuit is the dryzipper. You need to take care of it. Properly maintained, the zipper should last several hundred dives. Expect to pay $300+ for labor and parts for dryzipper replacement.
Inflater and exhaust valves are fairly easy to replace. You should get at least a couple hundred dives out of each if you take care of them. Some people get several hundred dives out of each. Replacements run $50-$100 each and are a straightforward DIY repair.
After several hundred dives, you may have to send in your suit for seam reinforcement or fixing small holes in the material. Cost of the repairs will vary based on the issue.
+ I read a post somewhere about undetectable leaks...how much could it cost to have a LDS plug a leak?
A new drysuit (less than 1 yr. old) with undetectable leaks should be sent back to the manufacturer for repair or outright replacement.
Most local dive shops don't offer drysuit repair services. The vast majority send drysuits back to the manufacturer or contract the job to another company that specializes in drysuit repair. The drysuit owner also has the option of going directly to the specialty drysuit repair shop or resorting to DIY repair.
Method of repair will depend on material composition of the drysuit. For example, pinholes in my Bare shell drysuit can be fixed readily with Aquaseal. In contrast, holes in my friend's Whites Fusion can be fixed with a heated patch kit sold by Whites.
You can always send out your drysuit for pressure-testing to find difficult-to-locate leaks. Cost of pressure-testing runs $40-$80.
+ I was checking out prices & tech suits aren't much more than the regular drysuits (a couple hundred). What are the pros/cons of a regular "sport" drysuit vs a tech suit?
Tech suits typically have a more abrasion-/puncture-resistant outer material. Although this makes the suit more durable, it usually comes with a heavier weight. Such materials might also take longer to dry. A simple bilam or trilam "sport" shell drysuit works great for shore and boat dives here in SoCal.
+ Is a drysuit more resilient than a wetsuit (in that wetsuits lose insulation over time)?
With respect to strictly insulation issues...
Wetsuit neoprene crushes at depth and re-expands upon return to the surface. Over time, such crush-expansion cycles decrease the insulating capacity of the wetsuit. With a shell drysuit, you don't have this issue at all. After a few hundred dives, you might consider buying new undergarments. Undergarments require washing every now and then, and some materials lose insulating capacity with each wash.
+ What sort of "wear and tear" issues come into play with a drysuit?
Beyond what I've already mentioned, you kind of need to avoid putting your suit in situations where it can get punctured. Crawling over sharp rocks is a no-no. Letting pets chew on the drysuit material when it's drying isn't a good idea. I'd warn you against kneeling on sharp rocks/urchins underwater, but you aren't doing that anyway, right?
+ If I was to take care of the suit and get one with good material doing half beach-entry/half boat dives, how many dives would the suit last roughly?
Several hundred dives. With the proper maintenance, you're only limited by how long the shell material and seams hold up. Some manufacturers warranty the seams for life. I have a buddy who has logged 500+ dives on his DUI TLS. Another buddy has put 400+ on his Bare. I've put 300+ on my Bare Nex-Gen. Another friend has put a 200+ dives on her Whites Fusion.
+ How heavy is the typical complete drysuit (boots, hood, gloves, suit, undergarments, etc) total?
Too many variables to consider. The "sport" drysuits are fairly lightweight and travel-friendly. Rockboots range from fairly light to heavy.
Undergarments are fairly lightweight.
Neoprene hood should weigh a little less than the standard wetsuit hood since it doesn't have the tuckable flap at the base of the neck.
You can wear wetsuit gloves with a drysuit, although drygloves work great and are worth the expense ($100-$160; the outer glove for my dryglove system [Viking Bayonet] may be replaced with a cheap $5/pr.).