it's a personal choice.
regardless of price or hp, track or street. i would always take GT3 over GT2.
you must make your pick

 

Those insanely low prices would make me nervous. You know what they say about if it sounds too good to be true. A 4K mi. 997 GT2 for $105K? Yikes

 

Gt2 all day long

 

The resale value says a lot. I wouldn't mind driving both. I miss a GT2 to drive around, you can't go wrong with either one.
Different characteristics

 

I've only met one GT2 who knows how to extract performance out of that car. In the right hands, it is a mean machine!

But from what I've seen, GT3 owners tend to be the hardcore track rats whereas GT2 owners are more like Ferrari owners (they have more $ than driving skill). The only difference is that the GT2 is more likely to kill them.

Hard to go wrong with either, but I'd go with GT3 because I favor response over outright speed.