I've got a booster plug fitted to my Triumph Tiger 1050, works a treat and changed the bike for the best. No more lumpy behaviour low in the rev range, or snatch you throttle response.
Last week I fitted the Kev mod to my tenere along with stage three air filters and removal of cat from stock exhaust. WOW, what a difference. Much more responsive and far smoother.

In summary, both options have worked well for me. The difference would seem to be in the packaging of the electronics and the price. The Kev mod is also adjustable whereas the booster plug isn't.

Yer pays yer money, yer takes yer choice !