I have an Gaming/HTPC rig(Aorus Strix 1080TI) in a large living room with a 1440p/144hz monitor/4k TV & 4k HDR Projector. This setup has taught me a lot about the limitations of cards, cables, and ports.
At one point the same rig had 2xG1 970's and was situated about 10' from a 3d display(1080p/120hz) that used dual DVI-D. Worked fine for that. When I changed cards to the 1080TI I suddenly got drop outs. Move the rig closer and switched to a shorter cable and all was fine.
This caused the rig to be about 20' from the t.v. and 25' from the receiver. Got several different 30' HDMI 2.0 cables(all rated at 4k/60hz 18Gbps). Would only do resolutions above 1080p at 30fps 4:2:0. One of the cables is an Optical HDMI I got from Monoprice and that one works great with our Phillips 4k player. BTW color depths are very vulnerable to the limitations of the cable. If you can't get to 4:4:4 or RGB 8bit(full) or 4k/60hz then that's a good clue you've got cable issues going on. At 4k these 4k/60hz cables are only able to provide 4k/30hz 4:2:0 limited on the projector. If I switch to HDR in games(RE7 and MEA) then major dropouts occur.
Meanwhile I have another rig in a smaller room that's connected to an 4k HDR t.v. via a 6' HDMI 2.0 cable and it happily gets 4k(3840x2160)/60hz/RGB 8bit(full) and HDR. I can also switch to 4:2:2 12bit but it 'seems' to render better at RGB.
So back to the living room rig. So I swapped the 6' cable I had in the smaller room, moved the rig closer to the projector and still no-go. Same problems.
What's a guy to do right? Well I found one of the first HDMI 2.1 cables on Amazon last week. Not labeled as such but by specs it pretty much is(48Gbps).
https://www.amazon.com/gp/product/B075N83B9X/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
Connected this to the projector and voila! Not only 4k/60hz/HDR/RGB 8bit full, but if I went to 1080p I could also do RGB 12bit full! I was even able to game at 4096x2160/60hz!. One of the resolutions this projector(UHD60) and this particular t.v.(older LG 55" non HDR 4k/3d) are capable of but this isn't available on all t.v.'s. Since the Strix has 2 HDMI ports I was still able to use my long run cable to send audio to the receiver in 7.1/24bit/192khz.
So the next challenge was that I had to move the rig closer to the projector but this meant it was now around 13' away from the current monitor(1440p/144hz/3D/G-Sync). Uses DP 1.2 but after what I'd already experienced longer cables I didn't want to take a chance on more drop out issues. Got this:
https://www.amazon.com/gp/product/B075N83B9X/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
Worked like a charm. Nice to have it right the 1st time and the hundreds of $$$ spent on my HDMI ventures.
My point is that cables can have a huge impact on your gaming experience. For those that have everything next to each other and are using factory included cables you'll probably be fine. As soon as you start moving things apart, especially over 6'-10' things can get tricky real fast. Save yourself some headaches and wasted money and as you spread things apart, use cables rated higher than what you need.
Which is cable type is better for gaming? To me it depends on the frame-rate. Most T.V's. only natively use 60hz even if they upscale to something ridiculously as high 600hz(saw some plasma's back in the day). So HDMI will suffice. 60hz at 4k is fine since most cards can barely do that at ultra settings anyway, at least for demanding games.
When I really want to see and experience fluid visuals then it's DP hands down. From 120-165fps DP has it covered on the monitor front and even if you get a display that's rated for those hz the manual will usually tell you that it's only available through DP.
The odd thing is that DP has really had some half-a$$ed implementations over the last 5 years. Before that HDMI had similar issues in going from 1.3 to 2.0. Now with 2.1 around the corner HDMI seems poised to be a very promising format again if consumer t.v.s truly begin to break the native 60hz barrier or monitor manufacturers adopt 2.1 in their displays. Until then DP 1.2 or 1.4 on monitor are what any hardcore frame addict should be looking at.