you should change the idea of BEST to cost effective. I use the Lacie rugged thunderbolt externals. Find them at the least cost either at Best Buy, Amazon E-Bay, etc. Buy the platter drive model and use it as is if you want. I swap the platter drive for an SSD and boot from it. works fine. Sleeps fine, wakes fine and runs fine. Been doing it this way for three years. I use the internal platter drive for data only but careful not to rely on it for critical data source only.
BTW purchase a Kanex thunderbolt external to get USB 3 speed instead of using the much slower USB 2 speed.
I also use the original Cal Digit thunderbolt dock with the Lacie and that gives me front facing USB3 port.
The Kanex I now use on the MacBook Pro 10 inch early 2011.
BTW best is not important because you are NOT going to get maximum SSD speed because of lots of factors. It will be something like write 275 megs/sec and read 350 megs/sec which is plenty fast enough. You platter drive is most likely 55 and 80