Massive. This is my opinion. I suggest you read up on it

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The M2B4 is not much better than an OEM non-LSD open diff. Under normal driving the viscous diff in the M2B4 acts like an open diff. Only when one wheel spins excessively more than the other does the diff "lock". It reacts to a spinning wheel rather than trying to stop it in the first place.
With a torsen style diff (found in the U2Q7, Quaife) it puts the power down much better. As soon as torque is unequal between the shafts/wheels the torsen diff will shift the power to the wheel with the most traction. IMO this will be much better for you as you will be dealing with a lot of power and torque. With this diff you should feel the car being pulled round the corner.
A broad comparison:
howstuffworks.com wrote:Torsen is superior to the viscous coupling because it transfers torque to the stable wheels before the actual slipping occurs.
http://auto.howstuffworks.com/differential6.htm
If you are interested watch this guys vids on viscous, torsen and clutch pack diffs, they are very interesting
https://www.youtube.com/channel/UClqhvG ... w3R48t9QXQ
I have a clutch pack diff in my 4G and it transformed/dominates the car

Having a good diff makes a lot of difference.