Not necessarily. Most seasoned wood is already splitting and cracking on its own as it dries out, so if you don't want to go through the trouble of chopping up some firewood then there's really no huge advantage to having splits over rounds. Both will burn just fine depending on how dry they are (which depends not only on where you store them but also what kind of tree species were used cut down). However, even though a big round log may look impressive once it's going in your fireplace or stove -and certainly heats things up more effectively-, most experts agree that smaller pieces contribute far less creosote buildup due to a reduced surface area. This means cleaner chimneys and less risk of chimney fires.