Snipers are a fun unit but generally take alot of focus/micro to be used to full effect but can be utterly devestating
Zeus are so cheap it compensates for the slowness they are very
cost effective
Zipper needs a buff imo
Crabe atm is lacking (hope the revert to old crabe goes thru) but not enuff to make arm kbot suck
Recluse (allterrain missile spider) is very strong and powerful for cost and all terrain to boot quite effective vs people bunching there units
Fido very good general purpose unit and also cheap
Cloaker kbot imo is arms main strength here the cloak isnt expensive and u can cloak a ton of kbots under one (around 50)
also emp spiders r great
Overall arm tier 2 kbot is quite strong but requires alot of mixing and combining and smart play to be entirely effective they are also generally cheap (cheapest cost for adv(tier 2 units) so it isnt hard to get a big force of arm tier 2 kbots
imo arm tier 2 kbot > core tier 2 kbot
in terms of vehicles at tier 2 .. Yes a smart player will try to go for a pene with faster units and dip round ur bulldogs..
Best way to use pene's effectively is not to use them till you can defend them properly and cause the enemy far greater casualties trying to kill one.
So say u got 1 lone pene and 2 bulldogs even 4-5 gators will get past the bulldogs and kill ur pene which isnt worth it..
But say u got a pene a few panthers and a mumbo watch the enemy try to get to your pene even with a huge ammount of raider units it will cost them to much to make it worthwhile..
Using a pene a support takes a bit of thinking as do alot of things in CA. Its mainly an arm thing it dusnt make ARM any harder to play they are just less direct about things but have other stuff to compensate like emp/cloaking.
Guard ur penes with mumbos/panthers if units getting to ur penes is a problem
and bulldogs are very good for cost i prefer them to reapers
Core might have a slight edge atm in some areas (its getting fixed) but tier 2 kbot isnt one of them

. And vehicles is always personal preferance