The Suunto desktop software does the planning portion of the dives and gasses very IMO. I used a Helo2 when I first started tech diving and it works very well. However, there is a couple of downsides to the Suunto implementation. The very first is that the RGBM model is extremely conservative even in P -2 mode & RGBM @50%, you will be in the water "forever"!!! Guys on the same dive would be out the 10-15min before me. That's a lot of extra deco gas. The second thing was that I could not match the RGBM plans to VPM-B and I was typically the only diver in the group with RGBM. Thus I ended up diving the Helo in gauge mode as BT and use VPM-B generated slates as the dive plan. The Helo also does not have a LED/OLED "always-on" display. The Helo2 display is also very small and info like dive time is not well presented. You will immediately understand what I mean the moment you dive Shearwater.
I was lucky to sell my Helo2 at a good price and used those fund to buy a Shearwater Predator (VPM-B enabled). I also now have the Petrel and IMO you cant make a mistake with any Shearwater product. They are fantastic, reliable, accurate, configurable and the only tool you will ever need. They also have on-board dive planners that also calc gas required for the planned dive.
I would NOT buy the Helo2 and only recommend the Shearwater for tech diving. Do not waste your money. Learn from the mistakes other have made before you. The Suunto computers are great OW devices and will surely keep you safe, but they are not the right tool for tec stuff, it has to many shortfalls.
