The syntax for DFSORT and Syncsort is similar in many ways, but there are also many differences. For example, DFSORT has many functions not found in Syncsort, such as PARSE, JFY, SQZ, IFTHEN, OVERLAY, UFF, SFF, etc. Since you didn't show the error messages you received with Syncsort, it's hard to say which function it was complaining about in your particular case, but I'd guess it was TRAN=ALTSEQ.
If you or anyone else on this list would like me to send you documents prepared by the DFSORT Team that discuss what we see as the advantages of DFSORT over Syncsort, as well as considerations for migrating from Syncsort to DFSORT, send me a note offline (firstname.lastname@example.org). Please put "DFSORT" somewhere in your Subject line to catch my attention.