Depends which wild caught "gt" you get. There's the common gold saum, white saum, and the not so common stalsbergi. The gold saum is the one frequently found in pet stores.
In my experience, the pet store gold saums frequently are pretty nice. Just be sure to pick out one with out defects (crooked spine, etc...). It also seems like the pet store ones are a bit more prone to parasites, etc... than the ones bought through reputable vendors (rapps, gage, conkel, etc...). This is likely due to the conditions the fish are kept under, though IMHO. And once you have the fish for a month or so, I wouldn't say that they are more or less prone to parasites. However, GT's in general do seem to be a fish prone to parasites and disease. So you have to keep up a good tank regimen.
Personally, if I were looking for a gold saum again, I'd just get another good looking one from a local pet store. Mine is turning out to be just great.
I've never seen a wild caught gold saum, but I'd like to. and the gold saum looks way cooler than the pics I've seen of wild caught white/silver and stalsbergi IMO.
What you probably consider a 'GT' is probably a Gold Saum - and for that reason, i'd say go for one for your lfs, save yourself not only money, but dissapointment when your 'GT' turns out to be a stalsbergi, and thats not what you wanted.
Also, provided you pick the best specimen from the store you will likely end up with a beauty anyway, Gold Saums are a beautiful strain of fish regardless of where they are from.
Just my two cents.
Here is the advice I was given.... go to the store.. look for the fish showing the most color, showing the most pattern and spangling on their tail and fins... also look at their fin structure and body shape etc... get the best specimen and you will likely have a good looking adult fish...
With this specific species, most will grow up to be great looking fish.....If given the time (they are SLOW growers, and it seems like most people just can't wait and get rid of them before the grow into the potential that most of them have). I haven't really seen any adult GT's that don't look good.