nothing in it really, both great calibers, great access to factory ammo of all sorts of brands, bullets, and weights, up and down the country.
I'd say pick the rifle that you want to own, that fits you, looks nice, inspires confidence when you hold it, and which is in great condition with no faffing about (bedding jobs, weird triggers, may need re-crown, re-barrel, etc. etc. etc. ), then apply for the caliber or caliber change.
Personally, just personally, I'd say .270, 30-06, .308 should be considered. There's slightly less factory 30-06 ammo kicking about in the lowland and border shops, but still available though. 'I' would go for a BRNO, Parker Hale, BSA or 'ideally' a Sako that has less than 1000 rounds through it, IMVHO. Look out for the BRNO/CZ ZKK's, they sometimes go for a BARGAIN because their owners can't get them to group - this is because the front tip can squeeze against the barrel and disturb the barrel harmonics. 20 minutes with sandpaper and a drop of oil to seal will have it grouping sub 1" in no time. I picked one up with less than 100 rounds through it, immaculate! paid £150 I think, first box were struggling on an A4 paper at 60 yds...a bit of sanding to clear the 'touching' area in the barrel channel and it shoots like a dream...man if the seller just knew, they'd be kicking themselves very very hard!