I've done extensive comparisons. For me it is impossible to get the ety foam tips as deep as the tri flange or comply foam, both of which i could pierce my brain with if i wanted to.
The ety foam still fit well and give me good bass, but the lack of perfect insertion depth for me causes a slightly brighter bump in the treble. Nothing bad, but i prefer the triple flange and comply. Comply is the most comfortable. I can put them deep, but the foam expands to fit, so it's comfy enough. The tri flange are usually ok for me but sometimes cause a decent amount if pain to where i don't want to use them for a while. They sound as good as the comply but a bit more treble presence. Not a spike or bump really, just a bit more overall brightness. With the comply in deep the difference is almost nonexistent and i prefer their comfort. Those are my chosen tips.
As for the custom molds. I went through microsonics and would never do it again. I'm on my fifth remake/remold and although slightly improved, they will never sound as flat, because the mold doesn't allow the er4 to go deep into your ears. Not even close really. So you might get bass with a good seal, but you also get a nasty treble spike. Rin verified this with measurements and many attempts as well. Some people may be happy with theirs, but i don't believe anyone will get the reference sound unless the get a different mold process or company that can somehow get the housing very deep. As for comfort i prefer the comply hands down.
The customs have a silicon that grabs the skin and actually irritates me a bit, fit wise they are ok, but nothing special in my opinion. Again, different companies may vary... I'd put the money into music or something more worthwhile personally. That's my take.x