They're the same thing, both made by LRP. These days you need to check that you have the right software loaded for your application. That's not an issue as there are plenty of people who know about them and will help you sort that out. If you buy a new one, then get the one you want for your racing (see LRP's excellent website that has full details of each one) then you'll be fine. If you get a pre-owned one, then find an LRP/Nosram expert at your Club or a National, who has the software updater on their PC, and they will usually sort you out.
LRP now offer logic board upgrades as well as software updates (that will fit both speedos), so it does mean your speedo will be good for a long time for a much lower cost than replacing it. HTH
