GIANT Boulder vs. TREK 820/3500

[Kevin in KY]

Trying to find the best new bike for my son...most of the riding will be neighborhood and light trails.

Does anyone have opinions on either of these bikes? All seem to be in the $220-$250 range.

What difference will 22/32/42 vs 28/38/48 chainrings make? Any?

Thanks for helping me add another young man to the world of bicycling!