Dear Mr Van Zyl
I dont recommend to do this or the other, finally you need to decide your upgrade plans.
Still, I want to provide some thoughts to consider:
Generally : An SP that superseeds a previous SP or HF should be more stable that the previous one as it contains all the previous plus some new bug fixes. However, as we all know sometimes new fixes cause new regressions (i.e. new bugs that were not in the previous version).
If the system is stable on SP135 or SP135 HF1, it might be a good approach to stay on that version and schedule a upgrade to SP136 when the SP136 HF1 is out. This is a low risk approach and reverting back to SP135 is possible in case it should be needed.
Regarding an upgrade to 16.0
Currently there is 16.0 SP01 and SP02.
For ASE 16.0 SP01 , PL03 (patch level) has been released recently and generally SP01 codeline seems to be quite stable now.
For 16.0 SP02 , PL02 has been released recently and PL03 is in planning.
16.0 SP02 provides several new features compared to 16.0 SP01
I am not aware of any stability issues in SP02 but wont be surprised to find that all the new features need some more stabilisation.
With kind regards
Tilman Model-Bosch