compared to the typical fast shredder?just curious how you would rate these guys......what if they can play any style competently?
I think they'd have to be very good players. I'm not in the business but it seems like a session player would have to be versatile and competent in several styles of play.
You mainly just have to be able to read music well and be able to adapt to any style, which takes both knowledge and skill.
They're proficient in many styles but tend to not be absolute masters in any, which is what's needed really. Exceptions always exist, like Nuno Bettencourt.

Quote by JamSessionFreak
yes every night of my entire life i go to bed crying because i wasnt born american
Most of them have extensive jazz backgrounds, making them better than your average rock or metal guitarist. Typically as fast as any shredder I've met, with better phrasing. Almost never as up on whatever extended technique is currently popular.
They have to be good at improvising in any style. They might get a lead sheet with just the chords on it, and they have to embellish that into a full song in as few takes as possible, so as not to waste everyone else's time.
They also have to be good at interpreting what the singer/producer wants to coax out of them. I remember watching an interview with some Nashville session guitarist. He said the producers would say stuff like "Do a Jerry Reed thing here" and he'd be expected to know what that means and immediately deliver.
if they are able to make a living doing session work, as in actually being a session guitarist, they have to be versatile b/c they have to play the style of whoever is hiring them.

as far as technique they may or may not be able to do shreddy stuff, depending upon what genre they are most strong in.