I find diving a twinset nicer and better balanced than a single. Having said that there are times when it is a hassle. For example Malta, a destination you ought to dive, is usually shore diving with rocky entries involving some walking fully kitted up. For typical UK or Irish boat diving a twinset is good if you can squeeze two dives out of it or if you are only doing one dive. Taking a 15 and a whip for a top up is a hassle otherwise.
I agree with those above saying to keep the single wing. For holiday diving it will be what you need. You can get twinsets on Red Sea boats but if you go to Indonesia or the Caribbean it all gets harder.
100 dives is ok, however maybe it is time to think about what sites you would like to dive rather than what kit you want to dive. This will lead to what training and equipment is required to make the dives and allow you to plan that.
Edit - you say less than 100, do you mean like 50 to 100 or like 20 something?