The pros of the 1970 are the high impact colors available. The cons are that it's not as good looking as a 69.
I agree with your pro, but disagree with your con. For MY tastes, the 70 Road Runner is the best looking of them all. The air grabber hood scoop that pops out of the hood is one of the coolest options EVER invented, IMHO.
Seriously, Pros are it is one of the most desirable muscle cars out there. Cons are that it is more costly to restore than a Chevy or Ford, but then again, the pros are you won't have a cookie cutter car like everyone else.
Overall design con is the rear window corners that damn near ALWAYS cause rust to start there - poor design. Early unit body construction could have been a bit stiffer, especially the hardtops - post cars are more solid.
So mostly it comes down to the individual car you are looking at. If it is in decent, restorable shape I think it is a no brainer...