I haven't been playing that long, but frankly I have to disagree with the Regenerator golem over the Cursed golem.
The regenerator costs a TON to use and operate, so while it can help you fight better in a straight up slug fest it will run you dry quickly. A Mk I fighter costs 100/100 to build. A regenerator golem losing 81k of health to save a Mk I fighter costs (81,200 health of fighter / 200,000,000 health of golem * 60,000,000 price of golem / 4 repair coefficient) = 6090/6090 resources to repair! This is for a simple Mk I fighter! (if this isn't the correct math then please go ahead and correct me). I would much rather build a few temporary space docks right beside the enemy wormhole, line up 10 engineers and just spit out my fighters who are rallied to the next system over almost as fast as they can be destroyed. Your manufacturing facilities can be relocated on a whim anywhere in the galaxy in about 30s at negligible cost, do that and you have 90% of what a Regenerator is already. In the end all a Regenerator is is a manufacturing facility with a 0 build time but a price premium that will make you fondly remember that the Merc Dock only has a 10x increase in price. This also means that if you aren't capped on Mercs, you are better off spending cash on them before on the Regenerator.
The cursed golem, on the other hand, shouldn't cost you much at all. You put it next to the wormhole while your forces are dukeing it out, it shreds things to pieces. This thing is simply the mobile gun platform of your dreams. Mk I/II/III/IV/V? We don't care, 10 of them die every second as long as this thing is in the system, and when its done you plink plink at the fortress and laugh. The "increased attrition rate" really means nothing, attrition is really slow anyways and Cursed Golems are several times cheaper to repair than the Regenerator Golem. This thing should never ever be at risk of dying, you can always run away through the wormhole it should be sitting next to the entire fight!
At best, if all you care about is a single decisive fight I *might* agree that the Regenerator is better (though IMO it should only seriously be used to keep irreplaceable things like spirecraft and other golems alive), but you WILL be run dry. You will certainly Curse (see what I did there?) the amount of resources you need to spend to get a Regenerator back in working condition after a big battle, and on Medium Golems the AIP increase will always hound you to the point where I think the Regenerator just isn't worth it. The Cursed Golem on the other hand is keeping your ships alive by killing your enemies, and its doing it without jacking up the replacement costs as much as 60 fold. Even in the rare case of the Regenerator winning a fight that the Cursed Golem lost, I'll simply pull out the Cursed Golem sitting right next to the wormhole, wait 3 mins while my fleet replenishes (thanks to all the money I saved by NOT using a Regenerator!), then go in and mop up the enemy force that is only half as strong as it was before. In the end, I still won using less resources and I'll be ready to fight again quicker since I won't need to completely repair that Regenerator.
TL;DR I'm disappointed in Regenerator Golems. Use them as a novelty to protect other golems/spirecraft in Hard or Easy Golems mode and on Normal where they give an AIP increase ignore them by all means.