Hi Andy,
The primary difference between these two BC systems is the adjustability of the secure harness.
The Infinity features our Cinch Quick-adjust harness which is quickly adjusted with a push or pull of the webbing.
The Eclipse BC features our Standard secure harness which is adjusted manually in small increments by moving the harness through the triglide points.
You cannot adjust the Eclipse standard harness size "on the fly" so to speak, so the Infinity is, by far, easier to adjust than the Eclipse. This is true for sizing the harness the first time, or while getting in and out of it when diving, and further down the road you can enjoy an ease of adjustment for different sized suits if need be... it's simply easier to use. This is a huge bonus over the Standard harness on the Eclipse BC.
Bottom line: the Infinity's Cinch quick-adjust harness requires far less time and effort to size/adjust and use, than our standard harness system and the deluxe padding components on the Infinity BC are wonderful for tropical diving comfort.
You'll also need to look at wing size on either system you choose. Typically the Infinity 30 would be the lift capacity of choice for warm water diving, unless your diving needs require more lift support. The 30-lb. wing is ideally sized/shaped to support Al 80 cylinders the best, although our 40-lb. wing works just fine as well.
You will also have the choice of a SS or Aluminum backplate. If you don't need to really minimize luggage weight while traveling, I would suggest the SS plate, it dives very well with Aluminum cylinders and offers a very balanced system.
Both the Eclipse and the Infinity BC's come with ACB10 integrated weight pockets as well.
Silent Planet is our UK distributor and has excellent information. Also, please keep an eye out for the Cinch Quick-adjust video manual showing how easily the Infinity BC can be adjusted. You can also visit Halcyon's main website for the manual or other product details.
Thank you for considering our BC for your diving! If you have any further questions I'll be happy to assist.
Sonya