Also Strong, why do you like Brinstar with Doc? And against what kind of player? Any kind of Doc info on non neutral stages will make me happy, because I never use 'em out of fear.
Sorry I didn't answer sooner; I went to bed early last night & school & johns. lol here you go
First, they won't be good stages for any character until you're familiar with the stage and comfortable taking your opponent there. Moving on:
Brinstar has a medium-height ceiling, and so Doc won't be murdered by Foxes up-smash/up-air or anything at like 70% like on Yoshi's Story lol. The blast lines on the sides are
somewhat close to the stage, so if Doc dies off the side it's not like he would have made it back anyway, so it doesn't really hurt his recovery so much. It also means that Doc's horizontal kills (so basically all of them unless your opponent DI's your f-air in) will be accentuated because sometimes Fox, Jiggs, Peach, Samus, etc. will die even though they could have recovered if it weren't from the blast lines.
The stage is also not flat, and so it will mess up shine -> stuff and general combos from most other characters. The uniquely placed platforms also give Doc good vantage points for edgeguarding (like what Dogy was saying with DK64's however to a lesser extent).
If you're fighting Samus/Link/Young Link (who uses those chars anyway lol), they won't be able to grapple recovery around your recovery like how it seems to happen on most other stages, to me anyway.
A lot of players aren't too familiar with Brinstar, so if you're good on the stage that gives you an advantage. The odd terrain can help Doc's pill spamming (they'll bounce at odd angles thanks to the slopes; this can mess with a lot of player's spacing), too. It's like cping a stage like DK64 or Green Greens, no one knows wtf to do LOL.
These reasons coupled with the fact that the acid helps Doc's recovery and doesn't help others recoveries as much (Doc can just like b-air if they're using the acid to recover, or even an fsmash/f-air if they're coming up from under the stage).
Personal experience with counterpicking the level seems to reinforce the reasons I mentioned above. I've even had some success vs. Captain Falcon and Marth on this stage LOL. I'll see how well DK64 works as a cp this Saturday, Dogy's post makes enough sense to me so I'd like to experiment with the stage.
also about the hitstun thing... like I said up there, hitstun is increased similarly to how knockback is. LOL chaingrabs wouldn't work very long if that was the case. Have you ever seen a character get down-air'd by Falcon or Ganondorf at like 70-90%? They're locked in hitstun for like a whole second or two LOL