currently it's all based on opinion.
3.40oe created by DAX
and
3.51m33 created by team m33 aka "the Russian coders"
basically they both have almost the same features. but they both have their own little bugs.
DAX's 3.40oe is a little older but on the other hand DAX has made plenty of custom firmwares so most people would say his firmwares are more reliable.
3.51M33 is the newest firmware created by an new group of coders. It is very similar to OE type firmwares and it is has the latest sony firmware.
In terms of your 3.10oe It's more unstable than both 3.40oe and 3.51m33 not to mention out of date. So I recommend you get something newer
Bookmarks