Wanted to follow up here-- ended up getting the Transcend Jetdrive 725 after reading some reviews. There's very little info on the Internet (think there was one solid review of a comparison between the 2) so thought I'd share my thoughts here.
Overall, the OWC vs Transcend comparison is of two very similar products. Neither has significant advantages over the other. To me, after reading customer reviews on a few sites of both drives, I saw a trend of OWC drives running into problems after some time. The Amazon reviews were noticeably better for Transcend than they were for OWC. Overall, I wouldn't hesitate to buy either, though.
Personally I installed my Jetdrive about 5 days ago, and it's awesome so far. I've not noticed one difference in speed in the system (it might be slightly faster than before) and the installation was painless. Sure one technically has faster read/write times, however the difference is real world usage is worth considering. It's so cool to be able to upgrade a rMBP part since Apple makes literally every other thing in these computers non-upgradable. Its sort of a little known thing since you know Apple's employees will never mention this option to any customer. It's truly a miracle some companies were able to engineer these and similar drives that are designed for exclusive use in Mac laptops.
