There is no question that flak is the single best counter against Corvettes in a pitched battle...however, it is really only safe to build flak that early in the game if the enemy is only building corvettes...if they are mixing corvettes and LFs, equal skill and equal economics will overwhelmingly favor the LF/Corvette fleet for several reasons:
- On a per cost basis, LF/Corvette fleets will beat LRF/flak fleets
- LF/Corvette fleets require less labs for TEC & Advent...
- LFs and Corvettes both are faster than flak and LRFs...in fact, LRFs are rather slow and have a very difficult time chasing down ships, especially across multiple gravity wells...the LFs and Corvettes are better at striking quickly, raiding planets, avoiding the enemy, retreating quickly when things are looking bad, and pursuing enemy capital ships...
- Corvettes have anti-light weaponry which is great for wiping krosovs and LRMs...this is very useful for expansion because the krosovs can bomb out your planets and the LRMs can outshoot turrets you build...the anti-light weaponry combined with the speed also makes corvettes excellent units for wiping construction frigates...
- Corvettes can shoot strikecraft...so can flak, but the corvettes tend to be better at dealing with bombers...combined with LFs, you have a very good force for dealing with early bombers (whether it be from LCs or carrier caps)...
Specifically in regards to flak, anti-SC units take a long time to build and cost a lot relative to their power...for the early game, those are two major liabilities...
In general, you are much better with LF+Corvettes early game than you are with LRF+flak...flak and LRFs definitely have their place, but there are only a few situations in the early game where it is truly to your advantage to build such units:
- Vasari SB rush on your HW....in this case, LRMs and Kanraks are definitely your best response unit....they have great focus fire and build quickly relative to their power...
- Cap heavy fleet....again, in this case LRFs are going to be the best option for quickly driving off the caps...that being said, you'll have issues pursuing the cap if it flees, and so having LFs still is a good idea...
- Enemy comes at you with only corvettes or only LFs...in a pitched battle, building the proper counter will help you...still, you'll have problems pursuing the enemy if they jump from well to well, so even in this case having the counter may not do you a whole lot of good unless you have a single chokepoint...