* Mares Puck Pro. Looks to be very basic. Least expensive unit. Likely prefer something a bit nicer.
* Aqualung i300.
Puck Pro's the cheapest, i300 might compute you longer no-stop times on a LOB dive schedule.
Geo's extra bucks for "less conservative" algorithm you say you don't want, and smaller form factor -- how your eyesight? I am not sure a Zoop would you get anything that i300 doesn't and Giotto's extra features aren't really useful.