I've got an old sunday factory I've had for almost five years, my brother just got himself an '10 glory after not having a dh bike for about two years. I rode his glory at thredbo for a day three weeks ago, he had my bike for a day while I waited for his to be delivered and built then drove down with it. The new glory is a lighter and better performing frame than the old glory. More like a sunday in action and ergonomics than the older model. Heavy plow bike? Not so much. Medium Giants are longer now, and the larges get longer without getting too tall at the head or seat tube like they used to. The large giant is better fit for someone about 183cm who wants a longer frame (me), than a large sunday because the seat tube height is less (17.5 inches vs. 19). The linkage and seat stay arrangement is wider on the new glory than on a sunday, and this bugged me a bit.
I don't know how the 4.1 vivid performs on the frame, because we swapped it for a dhx 5 and ti spring I had left over from another bike. The lower shock eye doesn't use a bush on this frame, the hollow tube of the co-pivot just slides straight through the shock eye. Seriously, I'd buy a glory dh1, and change the tires. Then I'd order a BOS because a top level shock would be the only thing you could do to get any real improvement out of that bike, and the BOS would suit the colour scheme better than a CCDB. We changed bars, stem, seat and put some old cullys on but that's just window dressing really. Also, download the rockshox technical manual and give the fork a service checking oil levels. I rode one boxxer that weekend on another dh1 that hadn't been checked and it felt bad.
The linkage and bearings in 07+ sundays are far better than the first ones, especially if you take the time to read the available guides and assemble it properly and locktite everything that needs it with an appropriate grade (243 or 262). You can get bearing kits with the inbuilt spacers from enduro, and pearce cycles in the uk do some hardware as well. This is fine if you've got an old one and know not to expect any support from ironhorse because they've gone under, but I'd guess that any warranty support and service would be lacking in the traditional sense for a new purchaser. So if you wanted any problems resolved in a shorter time frame or an easier availability of spares I'd go the giant as the easier of the two choices. If you want you can get offset cups to get the fork angle on a sunday reduced a degree or two if you think that would help, whereas you can't with the giant.
For spring weights, I can't remember what a dh1 one ships with, but we used a 450lb 3 inch nuke proof spring on the 2.75 stroke dhx and it was fine for a 90-95kg rider with the boost chamber wound all the way out. As for being 52kg and running a 350lb spring for a sunday, I'd say that's way off from my personal experience. I've ran 350 on 5th element, dhx, and 375 when using a cane creek. TF Tuned:
http://www.tftunedshox.com/info/spring_calculator.aspx tends to agree as well.
