This is one of those big topics because there's a load of information and opinions to sort through. Unless you're tech diving, any modern regulator will feel the same at recreational depths.
For each manufacturer, their top line models do tend to breath better than their mid-price-range models. But between manufacturers, you shouldn't really notice a difference between their mid-range models.
Servicing your regulator will depend on how much use it gets (based on a actual need) and if you want to keep your warranty (based on manufacturers' guidelines). Warranty can dictate servicing your regulator annually or every 2 years. In reality this doesn't mean your regulator will be faulty once a year is up (for annual service warranties) or after every 2 years (for 2 year service warranties) etc etc.
Do a google search: "site:scubaboard.com regulator service" and you'll find a lot of posts describing this in detail.
What you want to ask yourself is several things when purchasing a regulator:
- What's my budget?
- What are my service options?
- What's my diving environment?
- What's my gear configuration?
Budget is self explanatory. Service options is a matter of personal preference and convenience. To service your reg ("regular" maintenance or repair) you'll need an authorized dealer/shop to perform the work. This could mean an LDS that you could drive to or this could mean shipping it cross country if you have no authorized shops near you. So ask yourself if you would like the convenience of having a shop nearby that you could drop your reg off at, and that will dictate what choice of manufacturers you can buy your reg from.
Diving environment is an important one. If you're diving ice, you'll need an environmentally sealed reg. Here in Monterey, pretty much any reg will work, although I wouldn't buy a reg marketed for warm water.
You have 2 choices for regulator first stages: Diaphragm or Piston. In today's age, both breath relatively the same; both are balanced. There are still unbalanced regulators on the market though, in which case these will breath harder at depth.
Do a google search on the following if you're interested in knowing the difference
site:scubaboard.com diaphragm VS piston
site:scubaboard.com balanced VS unbalanced
Diaphragms are always environmentally sealed, Pistons have a portion of the first stage exposed to the outside water via equalization ports. This means it can receive silt and grit from the water, therefore it will be more important to thoroughly rinse your reg.
There are sealed Pistons however which prevent any exposure of the inside to the outside environment (just like a diaphragm first stage). Some are filled with lots of expensive Christolube therefore service will be expensive as you have to replace all that lube to environmentally seal your Piston Reg. Others are just sealed off entirely and use a equalization valve, such as those made by Sherwood, which run the same as other regs on the market, price wise (pistons and diaphragms).
Finally there's gear configuration. You'll want to see what you'll be equipped with and whether you can configure your reg properly. Regs have HP and LP ports (High pressure & Low pressure respectively)
SPG and AI transmitters (for air integrated computers) use HP ports
Second stages, inflation devices, and breathing devices use LP ports.
Meaning if you have:
- primary reg, octo, drysuit, SPG -> you will need 4 LP ports at a minimum to supply air to everything including your BC inflator, SPG will take up 1 HP port
On the other hand:
- primary reg, air 2, drysuit -> you will only need 3 LP ports as the Air 2 shares your BC inflator hose
For a further example
- primary reg, octo, drysuit, SPG, AI transmitter -> you will need 4 LP ports and 2 HP ports
If you get a reg with 4 LP ports and 2 HP ports, you can be set for almost any configuration you want. Having more ports can also make hose routing easier as it gives you more options, so I wouldn't suggest looking for the bare minimum.
The most you can get currently on the market are 5LP ports and 2 HP ports. There is no real price increase for more ports, but I just mention this because it can be important later when you start to determine your ideal gear config.
