I pinged one of our SNMP experts, and here's the response:
Which SNMP Perl library? UCD or Net-SNMP package? UCD and Net-SNMP are the same code base but Net-SNMP has a lot of internal structure changes, really a lot. With the changes, some bugs are introduced along the way. The two packages have a lot of difference though some main functions are the same. So, the Perl code in UCD and Net-SNMP may be different, maybe have some new bugs.
For Bigip server part, 4.5 and 9.0.5 there should have no difference on this part.
Bigip 4.x, we use ucd package and 9.x, we use net-snmp package.