My inbred feels like it's made from solid lead, but rides like a carbon bike. Prob because of the geometry.
If you're talking around 10lb difference then, yes, I'd rather have the lighter bike, regardless of suspension length.
If they're all within the same ballpark, then I'd rather have what suits 90% of what I'm riding.
There's a cheeky dh(ish) run on my local loop which would be bl00dy great on the Mega, but it's only about 10 minutes on a 3 hour ride. It's fun on the inbred, and the inbred copes with the rest of the loop much better(probably-based on supposition as I haven't ridden it on the Mega yet)