Probably budget constraints.

Multieffects are always complex, you need to spend time with the manual to learn to use them to the fullest and of course share opinions with others, helps a lot. =)

A simple guide here, Line 6 = great amp models (most of them do a little better than BOSS) lesser effects

BOSS = great amp models, more effects

IIRC, pod xtl has no harmonizer and some of the effects aren't as "smart" as what's available on GT-8 << the "smart" part i read it off somewhere so take it with a pinch of salt.