I posted a replay a while ago with a successful AGx3 and MGx2 opening; it works well in certain situations.
The only issue with a AG only or my build is a sniper opening and/or Scout Cars... with the new patch, AGs are more likely to lose a model or two at range against cons, ineffective at long range against an uncloacked sniper (Grens can do some damage), and die very fast to the Scout Car (as everyone has already said).
I'm interested to know, though, how can you survive without a T1 and going for 222s against Scout Cars? how do you not get owned
Going back to the OP, AGs seem to be more micro-intensive, as they are most effective at close range; thus, one must navigate around cover and zigzag to minimize casualties on approach to the enemy. Grens are a better balanced unit, but the LMG42 is much less effective at CQB now.
It really depends on what playstyle you and your opponent have, what BOs you're using, and how you want to use your units on the field.