I have an Ace 2 as a works phone as well as a Galaxy S2 as my personal phone. It has to be said that at 160.00 the Ace 2 is alright but there are a number of things I don't like about it. The first is the small screen which makes sending text messages a nightmare; especially with the standard Android keyboard not being the best.
The phone restarts itself regularly, usually every 2 days or so, for no apparent reason. This is especially annoying as I have set up a SIM lock so the phone reboots itself then won't recieve any calls or texts.
Also the phone has been known to die and need a restart during music playback. It will rarely manage a full album without switching itself off.
This is in stark contrast to my Galaxy S2 (which is a few months older than my Ace 2). The Galaxy S2 I have been pretty much 100% happy with; it is a 10 times better phone than the Ace 2