I have read all of the postings with interest. My personal view is that all Beethoven piano sonatas present serious technical challenges one way or another. These works, written throughout his life reflect his own formidable technique. Many pianists used to shy away from finding themselves in competition with Beethoven in terms of informal piano tournaments. Some very interesting and amusing research is available in these respects. At the end of the day it is down to personal taste. Choose a sonata you like the sound of/respond to as a listener and do not be fooled into thinking there is an easy Beethoven Sonata.
Clearly the level of difficulty varies greatly however, and I agree with the view that some sonatas are much more famous than others for a reason. Beethoven's own personal favourite was Op.28, but I have personally found it difficult to understand why. Of the more well known ones Op.31 no.2 is a personal favourite of mine, with plenty of technical challenges. It really is down to personal taste.
On another point, how anyone can say that they perfected Op.106 at first sight I find staggering! There are many subtleties in this piece that take years of practice to bring out. Generally, I would say to explore and try sonatas out. You will soon know whether you are drawn to it on the one hand, and whether a particular movement is within your technical grasp at the moment or not. If not, identify the technical problem and practise.
Some other favourites of mine which I have played for many years are Op.13, Op.26. Op.27 nos 1 and 2, Op.53, Op.110. I am also seriously starting to look at Op.111, in my opinion an even more challenging and rewarding sonata than Op106 which I have attempted too. By the way, Beethoven regarded his greatest work for piano to be his last one, namely the 33 Diabelli Variations Op.120. He managed to turn a really banal theme by Diabelli into sublime music, a set of keyboard variations surpassed only perhaps by Bach's Goldberg Variations.
Granted, a lot of this is my own personal opinion, reflecting my own personal taste in music, including Beethoven's music, however this is precisely my point; in the end it does come down to personal preferences. First fall in love with a piece and then be inspired and motivated to learn it, then tackle every technical obstacle as it arises. If necessary get lessons. No one is so advanced that they would not benefit from lessons from a pianist more experienced than themselves! I am a very experienced pianist and piano teacher but have taken extra lessons myself from top notch professionals when I found I needed an extra edge to my performances, and also when I could afford it!