The thing is if you have a drill already (ie most battery ones have some hammer) then most SDS is either going to be odd jobs of 5 minutes or less .. or .. you're going to hammering the crap out of it for extended periods (excuse the pun).
So the former - may as well go with a corded cheaper one (unless you have batteries and get a bare drill) to keep price down. In the later the corded means you're able to keep going. In the end there's only so many holes you can put in around the house!
Just make sure the SDS has a safety clutch and able 3 modes (rotate, rotate hammer and non-rotate hammer chisel). The chisel is good for hard tiles with a tile bit - but so is a hammer on a tile bit too

If you're coring or using longer drill bits then the safety clutch is a must (also helps if it can reverse rotation direction).