Ken -- time to also get that Mercian you've talked about for years now.
Regarding cranks: DA's are the only cranks I have not ridden out of the lot.
I'll get to Sugino first: I run 75's on one bike. They were my first real track crank and they've performed solidly over the years. Stiff and they feel burly and solid. They feel like they look. I'll continue to tout them as the best bang for your buck track crank out there. The Sugino 75 BB is smooth as butter -- the two together are one of the best combos ever. While cartridge might be worry-free, I love the feel of loose ball -- so smooth. Packed with Phil Wood, I only ever cleaned out the BB every 2 months or so. 1 month perhaps with a lot of rain, 2 weeks with snow. You should really try out loose ball sometime, I think a person like yourself would appreciate the subtleties.
Regarding the Grand Mighty, 11.4 has the last word on this:
Originally Posted by 11.4
What does the Grand Mighty have? Most of the cost is in the forging. Instead of something like three forging passes on the 75, the Grand Mighty has an amazing 26. This means it's much stiffer and individual parts such as the spider and the area around the pedal threads are much more resistant to impact damage or to flexion. If you fall (or get hit) hard enough to snap your crank, you probably have other bigger worries.
The finish on the Grand Mighty is mighty Mighty. It's a gorgeous finish and happens to be extremely resistant to corrosion, oxidation blooms, and the like. So it'll keep looking gorgeous while the 75 will look a bit punky after a while. And if you use toe straps, the clear anodized finish on the 75 will disappear in days, but the gold Grand Mighty finish will last a lot longer.
The milling of the square taper on the Grand Mighty is more precise (both done to size more accurately and also more precisely in the center of the crank) than on the 75. This plus the superior forging means you can take it on and off a lot more than a 75 before it doesn't quite go on as straight, and it is more likely to give you a truly centered chainring (people ***** about chainrings not being round when the problem is usually that the square taper was milled off-center, causing the whole shebang to be off-center, and no change in chainring will correct it).
It's up to you which one you get at this point. Personally I like the Grand Mighty and its durable finish and precision. Plus I do race track and it is quite definitely stiffer, although you have to put out a lot of watts and feel really good on an evening to be able to notice that difference.
My favourite cranks however, are on my daily ride. The Campy Pista cranks. I've had two sets because I've liked them so. They feel stiffer to me than my 75's, especially at the track. On the street, I'm not sure if I feel much of a difference -- but knowing what I've felt at the track, I can feel it on the street as well. Part of it certainly the way the two bikes are set-up as well and I've run the 75's and the Campy's on different frames to get a good idea of the feel. They feel more "alive" to me than the solidness of the Sugino 75's which feel also more "dead" or "dense". I attribute it to the way the cranks are forged with a thinner profile but a wider width in terms of how "spiffy" they feel.
The DA's are a crank I'm quite interested to eventually delve into, particularly for track as they are lighter, are forged similarly in terms of profile and width to Campy. They seem like a balance between Campy and Sugino.
But for now, I'm happy with the Campy's and 75's. Whatever choice you make, I don't think you'll go wrong with any of them, but to me, it sounds like you're going to be more intrigued and interested with the DA's.