You are going to have a difficult time of finding vendor to vendor
comparison documents on TSM vs. Veritas Netbackup or BackupExec that are
current and/or reliable.  It really takes a customer like myself that has
both to lay out what the issues are.  We have a very large Netbackup
implementation.  We finally arrived at Netbackup could not meet our business
requirements in the Windows environment and part of our UNIX environment.
We are now evaluating dropping Netbackup completely.  However, that said
your hardware configuration, business requirements, and size of your
environment have direct influence on whether Netbackup could be a solution.
TSM in my estimation can be made to work period and has compelling reasons
for being the product of choice.  For example, TSM has a deleted file
retention policy, a true Offsite Media management function, data object
management versus a tape backup orientation, etc.  Netbackup simply cannot
do these functions.  If you dig deeply and ignore the publications you will
automatically arrive at TSM.