Since I don't work for a shop I'll offer a different perspective. I started diving sidemount because I'm at an age where wear and tear has made it virtually impossible for me to reach backmount valves anymore. I found myself faced with a choice ... either quit doing dives that require doubles or find an alternative configuration that would allow me to do them safely. About the time I was considering my options I happened to do a trip with Curt Bowen, who was diving sidemount. It was the first time I'd ever seen a sidemount rig. After watching him use it, I decided it was a worthwhile option.
After looking into alternatives for equipment and training, I decided that I wanted to be trained by someone who dives sidemount all the time, rather than by an open water instructor who took it up as a sideline in order to add it to his repertoire of class offerings. So I traveled to Florida and took the class with Rob Neto ... in the caves of Marianna. Upon returning home I experimented with different configuration approaches that would make it easier to gear up in cold water gear, including drygloves. Shortly afterward I traveled to the Channel Islands, and decided to use that trip as an opportunity to experiment with using the configuration off a dive boat in sometimes rough conditions.
Some conclusions ...
- If you're looking for convenient, sidemount is not for you. Very little exists in terms of standardization, and the training spends a great deal of time on optimizing the rig to "fit" the individual. In almost every way, this is more effort than backmount. If, on the other hand, you're one of those people who loves to tinker with their gear, sidemount may have more appeal for you. In some respects, it parallels the arguments for backplate/wing ... it takes more effort to get everything just the way you like it, but once you do, it just feels so comfortable and streamlined.
- It's definitely not for the casual diver ... just more effort than it's worth if you only dive occasionally, or only do typical recreational profiles.
- I wouldn't recommend it for shore entries if you have surf or surge to deal with. If you need redundancy in those conditions, backmount single with pony bottle is the easiest option, followed by backmount doubles. In those conditions, the paramount consideration should be what you'd have to do to recover if a wave knocks you down on entry or exit. With sidemount you can always, as a last resort, unclip ... but that's easier said than done when you're getting pounded into the sand by waves. The one potential benefit of sidemount in those circumstances is that you won't roll.
- On a dive boat, entry is as much a consideration as exit. Depending on the boat configuration, sidemount may or may not be a reasonable option. Boats that have "gates" on the side for giant stride entry are usually built to accommodate a backmounted diver ... and the gates are often not wide enough to comfortably accommodate a sidemount diver. This means you either have to clip in at least one tank in the water or do a sideways giant stride entry. The latter isn't particularly difficult, but it does take a bit more care than the way you were taught in OW class. Backrolls can also be a concern, depending on your tank configuration and the boat.
Things I like sidemount for ...
- Solo dives ... while I can do these equally well with a backmount single and pony I do like the benefit of having both of my tanks independent, and equally useful rather than one for use and the other for bailout.
- Photography ... sidemount not only lets me get very low to the ground without touching the bottom (particularly useful for many types of macro photography), but because the "center of gravity" is where it is, it also makes it easier for me to get into and hold positions that are sometimes difficult to achieve in backmount.
- Go deep, stay long dives ... I'm talking dives at recreational depth where I want to spend a lot of time in the water ... 80 or 90 minute dives where I might hit 100 feet for a time and average 55 to 65 feet depth over the course of the dive. I live in a place where those kinds of profiles can be desireable at quite a number of dive sites.
In all of the above I'm talking specifically about open water diving at recreational depths.
Sidemount is more effort ... if you're shore diving you won't be walking to the water with your tanks on, but you still have to get them there. That means multiple trips ... and depending on how you do it, that can be a real PITA. On the other hand, it gives you some options you don't have with backmount if you're doing entries where you have to clamber over rocks to get to the water. The reverse is true coming out ... once again in reference to shore diving, it will take you longer to get out of the water. But, particularly when you're diving multiple cylinders, many people find making more than one trip to retrieve equipment preferable to carrying it all on your back ... particularly when that walk involves a hill.
There is no "formula" that determines which is better ... it depends on quite a number of things, involving your personality, your physical abilities, the dive profile, the entry/exit conditions, and how much effort you want to put into "optimizing" your configuration. It also, perhaps to an even larger extent, boils down to which configuration better fits what you see as advantages and drawbacks ... and we won't all see those the same way because of where we dive, how we dive, and why we dive ...
... Bob (Grateful Diver)
