SCUBA - Dive Computer Algorithms question?

[Yahoo_Down_2Nite]

I own a Suunto Cobra dive computer and really like the brand and model. Its easy to use, reliable and trusted.
I dive most weekends up to 20 metres on standard air although I will be going deeper and using Nitrox shortly and the Cobra can cover this also.

My fiance has taken up diving and really enjoys it - I think it'll be a life-long hobby (yeah!). She does'nt have a dive computer yet (decompression tables need to be used and known inside and out first!).

I would be happy with her getting any Suunto BUT I know algorithms vary by manufacturer and/or model?
SO.........If the algorithms vary then presumably the decompression stops etc shown will vary on 2 different computers on the same dive. I know the manufacturers err on the side of caution but if I were to buy another Suunto for her we would be relying on a single algorithm.

I guess my questions are...
1. Is it *entirely* safe to rely on 1 brand (along with dive tables of course)?

2. Do the decompression stop depth and times etc vary very much between manufacturers?

Sorry for the long winded question ;o)