Guys I am not sure if I want to open this conservative can of worms but I think I should.
I have a divecomputer.eu device. As a side note, this computer is not good - don't buy this piece of crap!!! It nevertheless runs Bühlmann ZHL16C which is probably recognized as the "best" algorithm for tec divers. I usually set it to 50/80. I also have a Cressi Newton (which has the same algorithm with Leonardo - Cressi's RGBM) that I use as a backup. (I also used to have a Leonardo at the very beginning).
Locally I usually do 2 dives back to back (surface interval typically 1 to 1 and a half hours) once a week or so, covid permitted of course. Dives typically are shore dives down to ~30 meters (100feet) and back. Generally speaking slow-ish descends / slow ascents.
Well, believe it or not, most of the time under these conditions and especially for the first dive Bühlmann 50/80 runs low on NDL before my Cressi. Quite often around 10 minutes earlier. If not mistaken I think I have seen up to 18 minutes NDL differences!! To be clear that's Bühlmann 50/80 being more conservative than Cressi's "very conservative" RGBM by more than 10 mins (under the conditions I dive).
Compared to 50/80, Cressi's RGBM becomes noticeably conservative/restrictive from the 3rd and even more for the 4th dive per day onwards (eg during dive trips) which I personally don't consider to be something too bad.
Another difference I find between the two is this: Once you start ascending Bühlmann is more generous and increases available NDL quite fast compared to Cressi's RGBM which seems to be clearing much slower. As an extreme example, if you put Cressi in light (i.e. a couple of minutes) deco, it typically doesn't clear unless you reach the stop depth and stay there for the given time. Bühlmann on the other hand clears light deco quite fast, typically on the way to the first stop depth.
To sum up, Cressi's DC with RGBM (Leonardo, Newton or their newer versions) are good and "cheap" computers that will serve most of the typical diver's needs for years. There is a very sensitive ascent alarm, but I've got used to moving my hand gently enough not to set it. Them being conservative is something relative and to me generally speaking being conservative is not a bad idea. Of course there are "better" dive computers out there for people who have the money or the specific need for the features they offer (eg gradient factors etc for tec dives).
Keep in mind that the best and most important dive computer of them all is the one you have between your ears (see brain). No matter which computer you choose, make sure you know:
- how to use it (RTFM)
- what it tells you and
- what it doesn't tell you
- how to respond
If you don't understand these, no matter how many $$$ you spend, trouble is quite often just around the corner.
Just my 2c as always.
All the best