Wow, umm gonna just get it runnin good then

 

They have more power potential it all depends on your budget, 200-250 rwhp is a reasonable goal with bolt on mods. Also contingent upon how bad it was treated on former owners.

To get in 250+ range requires better turbo, and head studs vs bolts, a really strong 6.5 is 275-300hp range.

Remember when comparing the 6.5 to others it is apples and oranges since the 6.5 is a IDI vs a DI engine, plus since no longer in production not a lot of "performance parts" out there and few vendors. Common rail injection really set the bar for high HP possibilities, my "built" 6.5 is capable of 18K tows I'm guessing now in the 275+Hp club I haven't dynoed it since 2005 when I was making 197rwhp lightly modified. Full ground up build blueprinted balanced engine since July 2013 with virtually every mod one can go without going VERY DEEP pockets say like the Heath Land speed racer 500hp 6.5L Diesel Race Engine

Upside for the 6.5 they have more power available, they are cheap to acquire and maintain a very good platform for the novice Diesel "gear-head" to learn and own.

I've been a 6.5er since 2000 and have no regrets with that choice both of mine will be around long enough for me to be buried in

 

For the 6.5 you would be lucky to get 300 hp out of it with just bolt on mods. Something's you can do are injectors, flashed ecm, exhaust, intake, turbo master ect