Low action guitar sometimes have more buzzing sound on the first few frets. So if you are looking for a low action guitar, play some E5 and F5 chords, if it buzz, the action is too low.
I can only speak for me here but it is often harder to do bends on a low action guitar. I play a lot faster on it but I won't do much bends. Good for rhythm guitar. High action guitar gives me more control over bends and so I be more expressive in my solos. This is my take on low/high action. By the way, the action can be modified later on too. Just make sure that if it's a low action guitar, there's no buzzing on lower frets.
As far as what to look when trying out a guitar, be sure the neck is straight and look for dents and scratches. Try the toughest chord you know, the one that gives you the most problem, this should give you a good feel for the neck (width, thickness). Is it easier of thougher to play than on your current guitar? Look for any loose frets and signs of dryness of the freboard. Bring YOUR amp, play thru YOUR gear, not theirs. You want to hear how it's going to sound with your stuff.
