This is a difficult one to answer. In fact there is no definitive. I suppose it is the "age-old" answer - "it depends" !
Your caution may be a good strategy. However, I would say it depends upon your environment and to investigate the features and "bug fixes" of both before you can make a decision. Even after this, you may still be none the wiser and that's why you get people from the other side of the fence who say "always keep up to date".
Which is why you always see the advice of test in a lab environment first. This is ultimately the "best answer", however I know not everyone can afford to or has the infrastructure to do this.
From the top of my head, I know from experience, that new storage features with 5.1 was my main driver and the following article may be useful if storage is an important factor in your environment :-
The other driver for me was SRM 5.1 which was a must and the new features and bug-fixes in 5.1 was a "no brainer".
I suppose you would need to do your own comparisons and to help you I have the below which may assist :-
If I come across anything useful further to this, I will post again.
Good Luck !