Spectrum vs. Guardian
Two main points. First and most obvious is the Spectrum allows you to use whatever second stage regulator you want. This is nice because you don't have to worry about getting the OTS second stage serviced.
Second is less obvious, but I'd argue more important for most people is that the mask has a flexible nose pocket so you can equalize normally vs. pushing the nose blocks up to your nose. A lot of people find this to be a steep learning curve.
For most people, I would not recommend even looking at the Guardian over the Spectrum.
I personally don't think Ocean Reef masks are up to snuff in quality compared to OTS.
@Lake Hickory Scuba is much more familiar with them and Bryan may be able to elaborate a bit more.
My personal FFM is the Poseidon Atmosphere. It is basically the AGA Gen 2 where the mask itself was designed by the same people but I think it is a lot more comfortable than the AGA. It also uses a Jetstream second stage which matches the rest of my regulators which is convenient. I love it, but similar to the Guardian, it does require nose blocks to equalize which is not as easy as the Spectrum, and for most people, it means a new first stage is also required due to the different IP that it wants.
Ford, Dodge, and Chevy all make a truck that will take you from point A to point B. Getting rid of all other features, it puts them all on the same level playing ground. Full Face Mask are the same. They protect your face from the environment, and have some type of breathing device that is integrated into the mask. The biggest concern I stress to divers who are transitioning to a Full Face Mask is, FIND THE PROPER FIT FIRST. Once you do that, then you can get the features you want. Picking a mask based off of features first then trying to fit it to your face is difficult. My face doesn't change size, typically speaking, unless I lose or gain a ton of weight on the spur of the moment. I have used pretty much all of the ones on the market, and truly like them all. As stated in other post before, my personal choice is based off of a working business relationship with certain manufactures, and the fact that certain mask fits my face better than others. The Public Safety Dive Teams that I dive on, are all mixed company, and we all dive different mask. I recently lost my salesman from Ocean Reef, but thankfully the business relationship with the company is still solid. Speaking strictly about Ocean Reef, they have 2 different sizes of mask. All the regulator second stages are built into the mask, different than the Spectrum from OTS (as mention by
@tbone1004 ). The biggest appeal for Ocean Reef (from our customers who are mostly recreational divers who dive less than 50 times a year) is the fact they come in a slew of colors, different sizes, and with the new Extender Package, you can customize the mask yourself without having to take it to a technician. The professional series of mask from Ocean Reef, are very robust, and most use rubber instead of silicone skirts, and steel instead of plastic or aluminum buckles. I can pretty much state all the same facts for all the other manufactures as well. The last bit of advice I will give you is this, if you are not planning on doing your own servicing, choose a mask that you can get serviced locally without having to send it off. This is a big plus, especially for small little adjustments that you would like to have made. It's much easier for the technician to do it the way you want it while you are standing there, instead of you trying to explain it to him over the phone.
If you are the type that dislikes buying from a shop, then I would still go by your local shop and see what they have. Learn about the mask they carry, and try several on before you buy. Then if you are still settled on buying online, base your decision off which one fit you at the shop and by what they carry, in the event you need to have it serviced.
After responding to this, I noticed your badge says Divemaster, and I am assuming since you are one ScubaBoard asking this question, you are an independent and that you are not affiliated with a shop. Not sure how dive shops in your area do things, but we offer 25% off across the board for any Scuba related purchase in our shop for Divemasters, Assistant Instructors, and Instructors, even if they don't teach or work for us. I would ask to see if your local shop has a similar program for dive professionals. You can always affiliate yourself with a shop, and then if they are like us, you can either get keyman pricing or a price that is slightly above dealer cost.