Key benefits depend on use. Locking converter reduces heat buildup, increase fuel economy - important for street use. As far as racing, I believe the 700R4 only locks in 4th gear (overdrive) - although this can be changed to lock up in lower gears. You aren't likely to be using 4th at the track.
Hard core racers seem to be split on using lockup converters. Some run non-locking, others use lower gear lockups as well, for better times. Goes beyond my knowledge. Current transmissions go beyond the days of the ‘glide and TH400 with non-locking converters. I think most of the 4th Gen casual racers with the 4L60E stick with a locking converter.
That said, I run a non-locking converter. I didn’t select it, the shop that built the engine did. But it isn’t a typical application. I run a TH400 with a Gear Vendors O/D, behind a 381ci LT1 making 800 HP / 800 lb-ft at the flywheel. A The converter is designed to flash to 5,000 RPM as the nitrous hits, and the car runs the length of the track between 5,000. - 7,000 RPM. Didn’t have the GV on it initially, but with 4.11 gears the engine was humming along at almost 4,000 RPM ar 70 MPH on the freeway. Doesn’t get driven on the street much, but when it does, 3,000 RPM cruising is a bit more bearable. The GV also comes in handy, keeping the engine from hitting the 7,000 RPM nitrous cutoff in 3rd gear at 135 MPH, when it's capable if running the traps at almost 140 MPH.
Use a manual switch for lockup on the street, try running with and without lockup on the track. Might pick up a 1/10th or two.