Open comb works best for me. Shave my goatee off once a year before the summer vacation and need just as many passes as with my normal shave routine.
Closed bars (including the slant) will get messy or clog up completely so you might need more time cleaning the razor than for the actual shave itself.
might not be a question of which razor but rather which blade.
I have very thick, piano wire like, whiskers and I use a Merkur 38c barber pole.
The blades that have worked the best are feathers, gillette yellow 7 o'clocks and swedes (no longer made.)
hope this helps
A Merkur Slant with a Feather blade. That's all I've been using for the past few years and any time I switch to a different DE or blade I fail to get the same results. I get BBS in 3 passes with a light touch up. My hair is thick and coarse, I get 3 shaves per blade. I could get 4, but the quality of shave at 4 isn't that great.
Open combs are good suggestions but beware that some are really mild (namely Merkurs).
In addition to the already suggested, you may want to try out an adjustable like a progress, slim or fatboy and open them up to a high/aggressive setting.
I guarantee you the R41 (aggressive version) will not be afraid of your beard.
I think I have a pretty tough beard and I can get any razor to work, but it may take more passes. I think the Feather, Polsilver, Astra, Wilkinson and Gillette Yellow blades cut more smoothly for me than others. Some blades feel like they are pulling the hair out. If I have more than a days growth or just want to do 2 passes then I'll use a Fatboy on 8, Fatip, R41, triangle slot tech or Weber as they seem to be more efficient than my other razors. I've only been at this DE thing for about 8 months though so my experience is limited.
I have very tough stubble - a Merkur Slant worked well, and a 2013 model Muhle R41 even better. I would have some experience before trying the Muhle, but those are my current 2 favorites. For blades, Astras, Polsilver Super Iridiums, and (unsure re: these) Voskhods or Feathers would be what I would try. Or Gillette Silver Blues or platinums/black, I believe (I may be mixing up some Gillette recommendations). Make sure your technique and lather are good.
I have a tough beard and I have many different DE razors. My most reliable shave for closeness and comfort is my Mergress/Progress using an Astra SP or Gillette 7 O'Clock Black. I set it at 3.5 for the first pass then dial down on subsequent two passes.
However...My closest and most efficient shave is using the ATT Titan R1 DE razor. I get a very close shave in only two passes, but I'm still struggling with technique with this razor and suffer a bit of irritation (user induced).
Beard preparation, as noted by TallyShave, is by far the overriding priority.
I always ramble- get a New Improved. They can´t be beaten.. I have very a tough beard and the model is cutting like nothing else. That´s my take- on DEs anyway.