Not necessarily, the cache and buffers on the chip may be the same depending on model. A couple years ago a 256/240GB was the sweet spot, as usually had twice the throughput, but the controller was the same for the 512gb so throughput was roughtly the same or slightly slower... that said, go for the space you really need. If it's the only drive in a laptop, go for at least a 240/256, but today I'd go for 480/512gb. (Note the 240/256 and 480/512 are pretty much the same, it's just the slack space is taken off the top/bottom for advertising, a certain amount of space on SSDs are reserved for handling bad sectors).