I love both bags, but when I have seen the OTG out in the wild, it reminds me of a large shopping tote. I prefer the tapered lines of the NF. Plus, you can cinch the NF and it comes with the pouch.
I had both. I sold my OTG and still have 2 Neverfull GMs that I use mainly for travel or meetings where I have to carry a ton. The causal style of the Neverfull suits my style more.