The most important thing to consider in the brand department is the track record of quality. If you buy a gun that malfunctions when you need it, it becomes an expensive chunk of metal. Do not spend time on what looks cool or what special forces team x carried to kill Bin Laden (they carried P226s by the way :) ).
I find that manufacturers with military/LE contracts are the most invested in quality. Gun companies live and die on the basis of these contracts and not civilian sales. A company that loses a contract because of quality will have a serious black eye that will cost them dearly.
Another indicator is manufacturers who back up their guns with lifetime warranties. Usually limited to the original owner and sometimes some small print on using steel cased ammo, these lifetime warranties could save you a lot of money should something go wrong.
If you are reading reviews on the internet, beware that all manufacturers have the occasional issue. Guns are complicated machines, just like cars, and sometimes things break under unexpected circumstances. Other times maintenance is overlooked and parts simply wear out. I have read people on gun boards complaining that their 25 year old gun with 10,000 rounds won’t cycle—they have never replaced the springs!!!
Obviously, I am a huge fan of Sig Sauer and stick to that brand for handguns. Other brands that I respect, in no particular order, are Glock (9MM only), HK, Colt, Beretta, S&W (M&P only).
Another thing to consider is the longevity of a particular make/model. If the gun you just bought is discontinued, your availability to keep that weapon serviceable will someday be impaired by the lack of parts. If the manufacturer is constantly taking models in and out of production, that is also a sign that you will have a hard time finding parts.
If you were to buy a 92F, 1911, G17, or P226, you are going to have access to plenty of parts for a very long time. There is also no shortage of gunsmiths who can work on these guns because they have so much experience with them.
1. Consider quality above all else
2. Look for manufacturers with military/LE contracts and lifetime warranties
3. Consider the long term serviceability of your weapon