Neighbor has the Islander 28 and it's a really nice boat. Having said that, current condition and PO's schedule of maintenance is key here. I, for one, think there's a very large difference in the motoring performance of an outboard and an inboard. I've had both and can say a diesel inboard was much better suited for my uses, which entails about a 2 mile motor out before I can really hoist the sails. Also, roller furling
up front is VERY much worth the extra $$. It just makes things a lot simpler, especially if you plan to do any solo sailing.
Most important, however, should be what's the real price for all 3 of these boats? You may be very surprised how much difference there is between "asking" and actual sale price. If that Islander can come down closer to the other 2, then your decision may get a lot easier. I'd go look at all 3 boats, let each owner know that you're a serious and qualified buyer (assuming you are, of course) and prepared to buy one of them, but you're looking for the best value. Get all 3 final prices, and then come back and share with us where you are then. Pics of all 3 wouldn't hurt either.