Zoop, but if you are willing to stretch the budget just a little more, Oceanic Geo 2.0.
Zoop: durable, user replaceable bat, easy to use, reliable, used by a lot of people, familiar in most reputable dive resorts (therefore batteries can be sourced)
Geo 2: user replaceable bat, longer bottom time, "wearable" in and out of the water (less chance of misplacing it or leaving it at home), safety stop readout in MM:SS as opposed to only minutes in the Zoop (it will literally count you down to the end of your SS...comforting to know especially if you are low on air), nato strap compatible (not sure if the Zoop is...you want this because rubber straps are notorious for breaking without warning), and most importantly, available in lady-friendly colors.
Also, Zoop will set off an alarm and reset your SS timer if you ascend "too fast" in Suunto's opinion...quite disconcerting on challenging dives (group ascent on drift, choppy surface, etc.). I understand that this is a safety feature, and safety ALWAYS comes first, but all I am saying is that it can also compromise your situation adversely when not dealt with properly. Of course, your mileage may vary.
I use a Geo 2, my wife a Zoop -- around 100 dives experience together on both. She will be switching to the Geo 2 this Jan "if the one with the blue face and the white strap is available"...did I mention lady colors? Sells $250 in leisure pro (Zoop $199).