How to choose the right institution for pursuing tenure-track?
Congratulations on your two offers ! As for your question, it's hard for us on this forum to gauge your choices. Tier 1 and Tier 2 are tricky categorizations (bottom of Tier 1 ? top of tier 2 ? area specializations ?). More generally though, it sounds like you're worried that getting tenure at the Tier 1 university is extremely difficult. 

But this is something where some data gathering might help. It shouldn't be too hard to determine the number of cases that went up for tenure at T1 in the last (say) 5-10 years, and how many were successful. This is in fact a legitimate question to ask the chair of the department. You can ask how the process works, and you can even ask current assistant professors if they feel they're getting good guidance on the tenure process. 

You should do the same for the T2 university as well. Then you'll have more specific information to work with. 

No one can tell you whether you will get tenure at T1 or not, but with this data you can get a sense of whether it's "yes unless you mess up" or "no unless you cure cancer". 

You can also try to determine which university offers you the best home for your research efforts for the next X years without worrying too much about what comes at the end of it. This is not to say that you should walk into a situation where no one gets tenure, of course, but your data collection should help with that.