AZAZA,
It reall depends on your pocket book and where it is located. Ie. water flying all over or dirty conditions. For example Baldor standard 100hp 1775rpm 460v 3ph 404T ODP motor lists for $3840.00. The same motor in TEFC lists for $6697.00. The super premium motors are correspondingly higher for both. Dirty operating conditions would definately prompt me to install TEFC. Costs more but in the long run will save money from contamination entry in windings and subsequent failure.
Poppeye