For the regs, the actual fitting in the mouth there are virtually all about the same.

The difference comes in the technology behind the internal workings of the reg itself.

I have to check but I seem to remember there are two or three basic types of technology behind the design of a regulator. Then there is the fine tuning the manufacture throws in to help sell it.

I seem to remember there being a feature of the ruby that allowed freer flowing air at depth, will have to check, but I can tell you after doing a dive to 35m with an Apex reg then the following week the same dive with the Ruby. The ruby really was much easier to breath from. I also bought the ruby because of the conditions I would be diving in, the cold north sea, the irish sea and the english channel. The silt and sand can be hard on regs and I wanted something that would last. You have to look at the type of diving and conditions you'll be frequently doing and choose accordingly.

My other reg, a posiden has a valve that you can adjust on the regulator to vary the "free flow" of air which is a great advantage when going deep, you need more air.

As to what I wear depends, when the water's warm, 14-18°C I just wear shorts in my dry suit. When it's cold -2 to 8° I wear a sort of lycra fleece shorty,inside my dry suit,very toasty. For really cold conditions there's a wool mix undersuit called a woolly bear. Only I've never tried one.

On one occasion we did a shore dive in winter with the air temp being around -3°c, yet the water was a constant +10°, it felt like getting in a warm bath, we didn't want to come out.

That's half the fun of diving, finding out what combinations works for you.