It kind of depends on which way the fancy takes you. If you want to follow the pack for practical reasons buy something in .308 because as others have said ammo is everywhere, however it won't be the same brand and weight and batch number so you will still be buying a fair amount at any given time if you practise with what you shoot or punch paper for fun. So, if you don't reload and have to buy a quantity at one time you may as well have something a little different to the run of the mill crowd. 7x64, 7x57, 6.5-284 or .280 would all offer big deer capability without being too uncomfortable to practise with or appear a big step up recoil wise from .243.
I'm not into shooting what everyone else shoots so I've a 6mmPPC, 7x64 and 6.5-284 in my cabinet and when I see ammo for sale I buy some or I have dies to reload. If you plan to reload in the future why let the current situation dictate all of your future considerations when they are not insurmountable issues.