Regeneration - The Namekian ability to regenerate limbs and health. There are two versions of Regeneration that EX Prillin can use, one being the Regeneration special move while the other is one of Prillin's passive Skills. The passive skill version restore some HP every turn. The Special Move version has EX Prillin regrow his arm to restore health though the Special move must be learned and requires ki for EX Prillin to use it.
Unlike his Fusion Dance counterpart, EX Prillin is not hypothetical as EX-Fusion allows people of different sizes and power levels fuse using the Fusion Dance as long as they are both wearing a Metamo-Ring when they perform the dance. Of course it should be noted that Piccolo and Krillin can perform Metamoran Fusion to fuse into Prillin in Dragon Ball Fusions.
Additional ly, EX Prillin is classified as a male Earthling while Prillin is classified as a Namekian. This implies Krillin's traits are dominate the EX-Fusion, while Piccolo's traits are dominate the Metamoran Fusion. However despite this EX Prillin retains Piccolo's Namekian ability to stretch his arms and regenerate.
Unlike Prillin, EX Prillin is also incapable of learning Kamehame Beam Cannon as Krillin is not a Full Power Kamehameha user as Kamehame Beam Cannon can normally only be learned by an EX Fusion formed by a Full Power Kamehameha user and a Full Power Special Beam Cannon user. However this limitation does not apply to Metamoran Fusions like Prillin and presumably this is due EX Fusions like EX Prillin being inferior to their Metamoran Fusion counterpart.