I have both. I originally purchased the VPM model because I thought I needed it to plan dives with V-Planner. After a few dives with that model, I did not like it for a few reasons. Main one is I have done so many dives on Buhlman, and have come to expect the deco stops that it provides. VPM throws me off slightly at times, and although it is close to Buhlman, it isnt. If I recall there were a lot more short deep stops. Since none of my buddies wanted to spring for the VPM upgrade, I kept ending up with a slightly different deco schedule from everyone else - Not a BIG issue, but I would rather my buddy and I's deco at least be at the same depth. that wasnt happening all the time. As others have pointed out, its still possible to do planning with V-Planner, and dive Buhlman saving the upgrade fee. YMMV but in the diving that I do here in South Florida, its rare that I plan a dive on the Hydro-Atlantic on sim software, for instance, and have my plan match my computers dive. It can come close, but so can Buhlman. So I say that is a moot point. Neither one will produce the exact numbers, because your dive depths will rarely match the software plan. At least mine dont. They are similar, but not the same. I own a Predator and a Petrel, and I dive them together when I do dives that have deco obligations, and dive the Petrel alone for standard NDL dives. For the record, if I dive the two computers together they match exactly. I would be concerned if they did not.
