You can still be 'realistic' with hicaps, just unload them to wind, simple.
I do however subscribe to the underlined quote below:
http://airsoftoperator.com/why-using-high-caps-is-for-your-bad-health/
"My conscious choice to handicap myself by using realistic capacity magazines is one for game play. It adds stresses and strains to your game. You have to count your shots, you have to carry more weight. You have to think things through. You have to be aware.
Reloads can change the pace of a battle. You wait for the lapse in fire to make your move, they add another element to the tactics. You can bait people into firing at you more, so they’ll need to reload sooner, giving you a window. You can use the enemy’s ammo as a weapon.
With high caps there is no lapse in fire, if you get pinned by a high cap, you’re going to be pinned for a long time. I would argue that high caps require a lot less skill to use effectively and I think many would struggle to argue against that notion. When you have that much ammo, it’s a lot easier to hose areas down than play effectively with proper tactics. Even high cap users that use semi only – that’s no better. In fact it means they take longer to get through all their ammo, so the time before they need to reload becomes even longer, making it even harder for anyone else to make a move on them."