If you're not taking long shot strings, prs,f-class, that sort of thing. Nor are you trying to get maximum velocity from them, a barrel will last plenty long.
The 6.5 will always have a touch more recoil because you're slinging heavier bullets. In a 6lb gun it'd make a difference if you're all in at 10lb might notice a difference. If you're building a target gun at 18lb+ or running a brake it's negligible.
If you want 1200lb of energy at 700yds you'll need a 6.5prc slinging 140gr or more. With a brake mine allows me to spot hits, it's loud but has flattened everything I've hit in the offside shoulder.