Here is some information to help decide and then some brand opinions of my own.
1. Make sure it is easily servicable in your area.
2. Spend money on it, you don't want to be in a position where you want to upgrade because you're not happy with what you've got.
3. Do research like you're doing now and through reviews
4.
http://www.scubadiving.com/ is a great place but they do not review all brands and models so don't just stop there perhaps search for user reviews on brands or models that have been suggested to you.
5. Chat to your Instructor/s or LDS, if you don't trust their opinions find a new instructor or LDS.
As far as brands go I'd go for Apex or ScubaPro. Apex because I've heard a lot of good stuff about them from all sorts of divers and reviews I read before buying mine and ScubaPro from my own experience and research.
Here is the scubapro sales pitch:
1. Produced in both America and Europe so parts are easily found
2. Great cold water regulators (I dive mine in temps sometimes as low as 6 degrees celcius and never had any free flow problems)
3. Backwards compatable for service kits (if you reg goes out of production the new service kits will still work in your older regulator
4. You'll receive upgrades that occur to the new regulator effectively improving what you have bought.
5. Life time warranty.
6. Usually a no questions asked return policy. (Got replacement fins after they were out of warranty. Friend dropped his dive computer off his balcony and returned it for a replacement, dishonest I know, but they replaced it no questions asked)
7. Cheap service kits in comparison to most other brands (here in SA anyway)
8. great quality product with excellent performance
I bought the MK16/S550 but I know the MK25 and MK17 are also great products. I'm one of those people that like the best so if buying again I would most likely buy the MK25 but at the time the MK16 was recommended as a cheaper alternative now I can't seem to find a good enough reason to upgrade.
Good Luck and choose wisely.