There may be some aerodynamic advantages in full scale planes between the two aileron types when you are trying to get the last little bit of performance out of a design, but in models it really doesn't matter. Build it based on what's easy for you to do, which usually means strip ailerons.

The fact that the nose wanted to pitch up doesn't necessarily mean the plane is tail heavy. It just means it's out of trim. If you are balanced at 25% chord (and are sure about that) then the pitching is a trim issue, not a balance issue. It could have been your engine thrustline is off, or it may well have been an incidence problem. In ferreting it out, don't make big changes. Make incremental ones so you can measure the results. A big change may cause other issues that you then have to figure out how to explain and fix, and of course, if you make a change in the wrong direction you'll just crash the plane and won't have any data to work with.