I think it would depend a lot on where you were in your anal play journey.
Agreed, for a beginner I'd say go with the Mood Naughty. I'm a COMPLETE newbie to anal and I just bought my first 2 plugs. I got the Plug of Lust (small) and the Mood Naughty (medium). I haven't tried the Mood yet but the Plug of Lust has proven to be a good option for a complete beginner like me. The Ultimate Plug, if you are used to anal, looks like it would feel the best though.