Senior Associate vs. Vice President vs. Principal for post-MBA PE?

it's just nomenclature.

Are you sure KKR puts MBA hires directly into Principal positions? I know people that went in as Associates.

An SA at BX has at least ~4 years of seniority (3.5 years if were hired out of college)

A Principal at KKR has at least ~5 years of seniority

These are not equivalent, unless at BX you would come in as a second year SA 

Senior Associate VP Principal (in most cases)

The nomenclature varies across PE firms (many don’t have VP). Principals are fairly senior - I would think of them as effectively a partner in training: they will often originate and run transactions and typically have an a number of years experience post-MBA.

CD&r cinven kkr hires you as principal post mba. Bx senior assoc (but the next promotion is principal). Tpg Warburg vp 

the above roles are all the same. Title inflation

As others have stated, these are all titles for the position immediately after MBA for these firms (and thus could be viewed somewhat interchangeably). However, different firms have varying lengths to Managing Director (or whatever title refers to the most senior level on a deal team) that would be interesting to hear data points on. 

For example: at CD&R, the titles go Associate -> MBA -> Principal -> Managing Director. How long does it typically take for a post-MBA hire at CD&R who enters as a Principal to get promoted to Managing Director vs. at a firm like Bain Cap that goes Associate -> MBA -> VP -> Principal -> Managing Director?

isn't it worse to come in as a senior associate (as opposed to principle) because then there is just another promotion in your way to getting to the top? even if comp is the same, I would assume not all senior associates at a MF make it principle, so isn't going to a place where you are hired as a principal a safer bet?