You should checkout about the nature of leadership people at that startup. In a startup you are very closely working with leadership on a daily basis due to low number of overall people. If these people turn out to be toxic, like abusing on every mistake, shouting in front of everyone, things like that, then I would suggest mnc for a happier life. In the long run, this toxicity will not be worth the extra income or the extra learning. If the leadership is good though, then startup all the way.
I've personally not done this, but I think connecting with startup's mid-level people on LinkedIn and asking them should fetch you good reviews.
Just my 2 cents.