OK, I'm jumping into the middle of a lot of opinions. Having spent my career designing a lot of pro audio gear, including work on some of the mics mentioned here, I have a few comments:
The difference between a textbook supercardioid and a textbook cardioid mic - in terms of gain before feedback is....about 2 dB. That's something, but not a huge effect - it will not take a horrible situation and make it good. Most mics that bill themselves as one or the other will, at some frequencies be a cardioid, and at others, closer to a super. A smaller diameter condenser capsule can get you a more consistent polar pattern over frequency than a larger diaphragm condenser or a dynamic - the Physics gives you that as a starting point, but how you design things and trade things off counts a lot in terms of the final result as well. If you are on loud stages in small places, with an ad hoc PA that goes everywhere, including back to the stage, and you have wedges cranked, and a singer with a not so powerful voice, a supercardiod might buy you a bit more forgiveness, but not all that much - it's one of a bunch of things you can do to manage a poor situation, but it's not a cure all by any means.
In other situations - particularly places with a good PA that doesn't spill a lot on stage, and in ears, supercardioids aren't really necessary - in those cases, the pattern forgiveness of a cardioid (and less proximity effect to manage) is an advantage. If the stage isn't too loud, bleed isn't really an issue - you have fixed the problem at it's source.
One specific thing I will comment on: Someone said with a condenser mic, you will need less gain. Yes, most condensers are a bit hotter in terms of sensitivity. That means you will run the input trim (or the fader) at a different place. That is almost never an issue in the real world, What can be is, with certain loud singers, you can run out of headroom with a condenser - if the "hotter" mic overdrives a stage in the signal chain before the trim control, you have something you can't fix with that mic - it's too hot. This is rare, but it does happen.
I'm not going to comment too much on specific mics - the interaction between a mic, a singer, and a FOH person has two very non linear devices in it (the people), and whatever they decide works, works. There are reasons to pick a certain mic for a certain type of voice, but there are no absolute things you can say. One of the singers I worked with for a number of years (doing FOH at a big church)) had a voice that was pretty strong on sibilants. The sound guys there had various techniques to deal with it, as most vocal mics have some treble/presence boost - that helps with most, but not all voices.
My approach was....I went to one of the Engineers that I worked with (I was his boss, so it was natural for him to say yes), and had him make me a vocal mic of a certain type, but without the resonator which gives that presence boost. Not every FOH person has a mic lab full of talented Engineers at their disposal, I know, but I did, and that worked very well. Interactions with various artists of note (and/or their FOH Engineers) gave us input that helped guide development of new models of microphones - a good Engineer needs to know their customers and what their issues are. I did a lot of FOH gigs, which helped me understand how to do my day job better (my day job also made me a better FOH person).
The topic of "sound guys vs musicians" comes up here often - in this context, that sound guys might want to use what they are familiar with. And you want to use a mic that you are familiar with. So, we have two "strong willed" people that come into a situation, and they have to co-exist. I'm a musician as well as a FOH person. I see this kind of thing from both sides. The thing that fixes this problem is communicating clearly and being flexible. Yes, the FOH person you are working with may not be the guy I know who has done FOH for decades for big touring acts - he's probably not that good, or that experienced. But that highly experienced guy I am speaking of got schooled by an artist once - the first day, he suggested (the guy has sold tens of millions of albums but has a nasal voice) a different mic. Oops. He hadn't established credibility and trust, and it took him (one of the most talented FOH people in the world) a year and a half to get to where it was OK to swap that mic out.
You are probably not an artist who has sold tens of millions or records. The person doing FOH for you is not one of the top FOH people in the world. Neither of you has enough power to be able to demand that things be done your way - you need to throw away that mindset. If you want to sound good, that person doing FOH (the one with the limited talent) has some experience with certain pieces of gear. If you go in and insist that that person has to work with a piece of gear that they are not familiar with, you now have put the person who determines how good you sound in a headspace that's awkward for them, and their limited talent added on top of that means...you have increased your chances of sounding bad. That's just not smart.
If you walk into a situation where there is time to have a discussion about what mic to use (many times you don't have that luxury), you can say "I have a lot of experience working with my XYZ model mic...are you OK with trying that? At this point, you shut up, and listen - what you can say has been said, and you should not push things if they don't say yes. If that person says no, then no is the answer. If you play the same place a lot, you might over time establish enough trust to experiment (I, as a bassist, have worked with certain folks enough that they know whatever I bring in on my pedalboard, it won't mess things up), but the first time in, I'd be very cautious.
You don't need it, but also, you don't specifically need to NOT have it neither.
