Just in case others are interested in running Enemy Within using TOW RPG, here are my conclusions thinking about switching my currently running campaign:
WFRP:
Going by XP and Sessions in TEW, our campaigns pace is closer to the slow/many sessions estimation, because I tend to fill the campaign with side tracks and use a lot of the companion modules. I would assume 160 sessions is realistic for us. We are currently at 40 sessions and 3000 XP in WFRP. So we might end at about 12k XP. In WFRP it is no problem spending those without the characters getting to similar due to talents being taken multiple times and the rising costs in advancement for a very large number of talents.
TOW:
Assuming the same number of sessions characters should end at 160XP and just as many endeavors. I would assume that it is not always possible to go one endeavor per session due to campaign pacing but it should not fall too low for the game to work, I go with 3 per 4 sessions resulting in 120 endeavors.
A human needs 114xp (assuming no career changes!) to max out all characteristics. The book gives access to 59xp worth of talents, not all can be taken by everyone and nearly none can be taken more than once. Having 46xp left for talents means most characters will run out of choices.
Skills is a bit more difficult to estimate due to the reliance on the current characteristic value. I did some quick calculations of the number of endeavors necessary for a single rise depending on current characteristic and skill level and assumed characters spread their advances more or less evenly and the result was: Skill Level 5 at 96 Endeavors in all 18 skills. Level 6 in all skills at 192. That might be a bit off, but in the end the characters would all be experts (Skill of 5 or up) in everything they even remotely care about.
Conclusion (for me):
Running TEW with TOW RPG is currently not really viable, unless you limit advancement, which is not a good idea in my opinion.
This is not meant as criticism of TOW RPG, I would have loved switching the campaign over due to the extreme fiddlyness of WFRP, but unless your players don't care about mechanical character progress, mine very much do, I don't think it is currently a good idea if you run the campaign at average to slow speed.