dhroser- I will try to make this a short answer 'cause there is a very long one that would explain much more about the different systems... for my personalt credentials I shoot regularly with all three sytems and with the top end models of each. I can only tell you about my very own experiences and this has to do with a lot with what LIKE...
1. there is no camera out there that can do all perfectly well or I guess we would have it all by now

2. all three camera brands are perfectly well able to deliver outstanding image quality
3. image quality depends mostly (beside the photographer) on the lenses you use- so don't go for a top camera with crappy lenses or you will regret it
4. Canon has been the camera of choice particulalry for landscape- and (!) I said "particularly" and to some extent for wildlife as well
5. Nikon has been in the past mainly associated with reportage style and low light photogaphy- so good for your gigs
6. Sony has off lately become a serious contender- even so serious that it appears that some Canikon users are now considering the system for the first time
7. Noise issues are very relativ: there are very good programs out there that can deal with that problem. It also depends on carefully shooting style. There is a lot out there on the net that explains how to set each of the cameras to optimally perform in low light situations. Nikon has the edge on low light (for your gigs) at the moment but one more persone trying to tell me that you can blow up a 25600 ISO shot of the Nikon camera for exhibition purposes and I will turn into a killer- this is rubbish!
8. The lens line up/and quality of lenses is IMHO best with Sony- Nikon has some problems on that front- Canon comes very close but I prefer CZ lenses and not for the name!
9. So it comes to handling and preferences: flash system with Canons are purely crap (IMHO)/ Nikon is the best on that front with Sony following closely. I personally hate the menu system of the Canons and love the handling of the Sony.
So in a nutshell: for me it would be between the Nikon or the Sony. Now one other point between these two: Nikons tend to accumulate very easily dust on the sensor- so more cleaning needed. On the other hand you can use the Nikon as a hammer- it is very well build!
My advice: go to a shop and really handly both. If you can affor financially rent both systems for a days and see how you get on. Really it depends a lot on handling and how you like the "feel" of it; also on how quickly you get used to the menu systems and so on.
Last point over -exaguration or not: the Cano does have a problem and until it is not clear what it is I would not spend all that money. For me it is not a question of how big the problem is but the fact that very like Canon knew about it but could not solve it. It appears that this little black dot issue is a sensor problem and after the AF problems with the DsMKIII which was played down by Canon for a long time before finally admitting this problem I just don't trust the company- but than... that's my very personal opinion. (If I would own that particular Canon model I would also not be amused about the fact that Canon brought out the new 5D MKII with literally nearly identical specs just a "couple" or thousand pounds cheaper...)
Good luck with your decision!
Stef.