I tend to agree with everyone, Lycra is a LOT better... A little breezier, but overall more comfortable.
Sometimes you just don't want to show *everyone* your assets, though.
Another thing I've noticed about MTB shorts is because they're baggier, they handle crashes into sticks, etc better than lycra. Lycra can tear, leaving you *em*bareassed.
If you want the protection and breatheability of lycra shorts with the stick-shedding ability of mtb shorts, you can try wearing real road shorts under very light board shorts, but they still get caught on the saddle, sometimes.

REI also has padded underwear, that don't shift so much, but also go under whatever shorts you want.

You *will* be judged as a newbie by some, but if *you* are comfortable in what you're wearing, what does it matter to them? Just get good and smoke 'em in their lycra, then tell 'em that training with the extra weight and wind resistance has done you wonders.