Whether they have the home field advantage or not, the Charmed Ones would win hands down.
When factoring in the ten year power boost from Morality Bites, the fact that they'd be outnumbered doesn't matter at all, in my opinion. In the future we saw Piper freeze a whole hell of a lot of people (and birds she hadn't even intended to freeze, I believe) without even exerting her full strength. All she would have to do is freeze practically everything insight, and then all four of the sisters could pick off frozen zombies, lickers, etc. one by one. Same goes for Prue's power boost, one flick of a wrist and there goes dozens of zombies flying away.
Although I hate her, I do think Phoebe would be pretty useful in the fight. She may not have the best active powers to fend off zombies, but all throughout the show she was always portrayed to be the best spell caster, or at least the best spell righter (she was even the one who taught/told Prue how to cast her first spell, I think?) She's been known to think on her feet, as well, so I wouldn't be surprised if she whipped up some quick offensive spells right off the bat to help even the tide (similar to how the sisters did when they were faced with the Warlock from the future, who stole the book, eventually vanquished Phoebe and Paige, etc. - I forgot the actual episode name. They came up with a whole new set of offensive and defensive spells right then and there).
Prue and Piper would be the strongest fighters all around, I'd think. Prue's telekinesis would be able to keep zombies at a distance, and she'd be able to use her surroundings against them, like pretty much everyone else has said already, hah. Piper would obviously be able to freeze and blow up - but I wouldn't just restrict her powers to long range birds and things like that. If the battle field is Raccoon City, she'd be able to blow up cars, pieces of buildings, power lines, etc. as well. All in all everyone would be extremely effective in vanquishing any Resident Evil creature that they came in contact with. Paige's orbing would clearly help, not only if they were forced to retreat, but she'd be able to orb things to the Underworld, too, just like Black King said.
I'm not sure if you can pick an individual sister who'd be better suited to face off against Nemesis (or any other Resident Evil big bad), simply for the reason that all three of them (I'm counting Phoebe out because even with her spell casting or what not, pretty sure Nemesis would pound her skanky ass into the ground if she didn't have help from one of her sisters) would have very different ways of fighting. I see Piper freezing Nemesis - and then blowing him up, if that didn't work, she'd at least be able to blow up parts of him, and his weapons. Prue would just slam him around with her telekinesis, or take his guns from him and shoot him to death, hah. Her battle techniques are virtually endless simply because her power isn't restricted to one set use, she can use it to do a lot of different things. Paige would either orb him away, orb away, orb his weapons away, etc.
The question is whether or not the sisters would be fighting their way out of Raccoon City, or fighting through the city in search of innocents. That would play a huge role in how the sisters fought. If they were looking for innocents their main objective would be to find their innocent(s), and protect them. If no innocents were involved, they'd be able to unleash all of their power without fear of hurting anyone else.
Sooo yeah, either way. Charmed Ones would dominate.
