I would seriously recommend neither for a person who wishes to stick with job .... although I said Part time for the polls due to lack of choice

...
In my opinion you shud go for Executive MBA programme , and I think most top tier companies are offering exec programmes...
IIMC has one I believe which wud be cool for people like you .
I think its a good decision to not ditch a job to pursue MBA if you really like what you are working in ...
afterall MBA is gyaan , nothing like it if you work and pursue MBA...
good luck