I race indoors on a fairly tight track (18x12 m) and have run all the different front drive options over the years. I started off with a diff, it was easy to drive and gave the car a very neutral feel (almost too neutral for me). Then I used a one-way which was faster but took some time to get used to as it was much more difficult to drive. I continued with the one-way until the power increase that came with the brushless motors made it too difficult and I switched to a spool.
The spool is just as quick but requires a different driving style. As the front axles are locked together there will be a greater tendency to understeer on corner entry but by the same token there will be much better drive on corner exit. It is certainly true that the spool is much harder on the front drive train - you definitely need steel driveshafts as aluminium will either bend / break / wear out far too quickly. The general wear rate on the components is also increased, but not to an unacceptable level.
One option that I've heard that gives similar characteristics to a spool but is a little kinder on the drivetrain is to use a gear diff filled with putty. That way it pretty much locks the front axle but the putty has a small amount of give in it that a conventional spool doesn't. The trade off of course is that it'l have a significantly greater mass than a spool.
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