We build the TBB binaries using Intel C++ Compiler. Different compilers may generate different instruction sequences apply different optimizations, so resulting binaries will most probably vary (in size as well), andit is not a sign of problems. For example, function inlining may lead to significant size increase.
Normally, we see no need to rebuild TBB and replace the supplied binaries. Anyway, you have already rebuilt it :) There should be no difference in functionality between the two sets of binaries you have. There could be some difference in performance or overhead, but it's hard to say apriori which binaries will better work for/with your application. So use whatever binaries better suite your needs and criteria.