I was also already on HRT before I even started electrolysis, so I can't compare either. But in my experience, it really isn't that painful at all. Granted, as leacobb said, everyone's pain threshold is different, but I still find it hard to believe that it would be ~that~ much less painful if I wasn't on HRT. It's barely worth being called "pain" as it is. More like "intensely sharp but brief discomfort," like the shock you get from static build-up, and not even as bad as that, really.
Obviously you know your own threshold for pain better than anyone else, but if I were you, I would make HRT a priority. Since you don't know for sure that HRT will make electrolysis significantly more painful (it's supposedly a bit different for everyone), it seems poor sense to delay HRT solely for that reason. And in my personal experience, four months is a really long time to wait...
I think the warning against undergoing electrolysis while on HRT is generally directed at people who haven't started either process and are planning to start HRT before starting electrolysis (that was the impression my electrologist gave me). You're probably better prepared for any changes that might occur, because your body has already had some time to adjust to the experience of electrolysis and the level of the pain you receive. So even if HRT does increase your pain level slightly, your body can probably readjust more quickly than someone who is new to the process.
Good luck.