What's wrong with "tricky technical problems"?
Overcoming these is how we make progress. Anyhow, to answer your questions.
I've played Nos. 5,6,9 & 24. All of the first movements are pretty manageaable. The F-sharp has a couple trickly left hand passages, but they are only a couple bars long. (The last run in the left hand is a little awkward and requires some un-intuitive fingering to work, at least for me.)
(Edited: Had incorrectly entered No. 14 when I meant No. 24.)
I know the E-minor has a couple of wide stretches in the left hand that some people have a problems with. (Ask Sam about that one.)
I am personally not very fond of either of the two G major, but that's me. Listening to them and looking at the score, there doesn't appear to be anything too difficult with either one.
Which brings us to the E-flat. It is a terrific piece, large scale, sweeping and very representative of middle Beethoven. If I had to choose that would be the one. (Of course, I probably would have jumped at learning the Waldstein.)
If you intend to eventually learn the whole sonata, the E-flat does pose some considerable problems in the remaining movements, both technically and musically. And the F-sharp major (which I am currently polishing for performance), has a really tricky and awkward second movement. It looks easy but it's not. Trust me.