Out of those two I'd buy a .308 for deer every time. If I was new and wanted to do a bit at the range, I'd buy a .308 for that too. If I wanted to mash up carcasses with what is, in my opinion at least, the worst deer calibre ever... I'd buy the .243!
It's not about power. Both will kill anything in the UK and beyond. For me it's about velocity. The .243 does a lot of damage to deer and if you're putting a lot of shots down it on the range because you're new and loving it, it will also burn a barrel out considerably quicker.
It's not about power. Both will kill anything in the UK and beyond. For me it's about velocity. The .243 does a lot of damage to deer and if you're putting a lot of shots down it on the range because you're new and loving it, it will also burn a barrel out considerably quicker.