To be perfectly honest, I prefer warp points to unlimited FTL, unless it is limited to use outside of solar and planetary gravity wells, because otherwise you (or an enemy) could just warp a fleet of planet-crackers into low orbit, drop their payload, and then bug out. Even then, it messes with defensive strategy, killing the point of having static defenses that are anything less than massive belts of weapon platforms and minefields around the whole system.
As for enemy planets, I would always just wreck them unless the enemy fleet was already incapped, because a ground war gives the enemy a chance to retaliate, while a glassed/cracked/irradiated world not only means that they can't restock, repair or replace their losses, but that (on a large scale) that their entire civilization has been destroyed, which, assuming a more advanced AI with specific characteristics for races and commanders, could mean a revenge-driven suicide run, but could also mean surrender or flight in an effort to preserve the rest of their species. Which is frankly more interesting than killing their fleet, idling away a few months while the ground troops do their work, and then going "hooray, more industry and unhappy population to manage."
Imagine wiping a civilization, but having parts of their fleet escape, and then a few decades down the road they come back with a rebuilt fleet and new technology and start wrecking your shit.