Hi - Thanks for your reply.
Here is your timeline as I understand it:
Graduated in 2011 from NYU
September 2011 - March 2013 1st job (1.5 years)
April 2013 - Present 2nd job with recent promotion (approx. 1.5 years in September 2014)
The thing is that the adcom is looking for at least one recommender who has a certain amount of experience and who is ready to go on the record and vouch for your professional performance (and more importantly your potential) as it stands right now (not so much 1.5 years ago). The adcom needs someone to judge your current work style, values, strengths and weaknesses - and although your client or former colleague may be able to do some of that - only your boss can really give you a completely thorough recco. If I were in your shoes - wouldn't feel very comfortable applying to top 10 schools without a recco from my boss.
But let's go back. You said you are 24 now and that you just got a promotion (with more managerial responsibility). Without having seen your resume or knowing anything about the schools you are targeting or your GMAT...my honest advice would be to wait one more year and then apply.
You will have 1 year+ of experience in your managerial role and more exposure to those big projects you mentioned (that will make for some great essay topics as well as material when you start interviewing for internships/jobs).
You already have a great relationship with your boss and one year from now I'd assume you would be in a much better position to ask for the recco.
If you wait a year you would be about 26 going in and 28 coming out - the ideal age as far as recruiting goes.
If you want to email or PM me your resume and keep discussing feel free.
fxmbaconsulting . com
Senior Admissions Consultant