I need a quality Reverb VST

[deRaNged 4 Phuk'dup]

Not to take any attention away from the original question, but what do other outside reverb plugins do that stock plugins cant do? Do other ones have more features or do they somehow sound better?

Depends on what DAW you're using. Most are released with competitive plugs that change to keep up with the current quality of music production. I think there's a placebo to 'stock plugs" that convinces people they need better 90% of the time. There are seasoned engineers who don't care enough to outsource from things that come stock, same time, there are others who rely on a specific reverb(hardware or software) for everything.