Portable SSD

Hello everybody.. i need to get a portable OS for work/study reasons, so i was struggling between build a live USB pendrive or get a portable SSD(128-240GB). For everyday usage it seems to be better to have a portable SSD... but i noticed that a real portable SSD is much expensive than a normal SATA and i wandered there are some adaptor from SATA to USB. Are these adaptor doing bottleneck from SATA to USB?

Anyway, if you suggest some smart methods to have a portable OS with good performance, i'm here for this..