If you're thinking about which you want on one of these tractors, here's my take.
I started with a 425 with a 60" deck... grrrrreeeeeaaat deck, built like a tank. If you can tear one of these up, even after years of hard abuse, you must be a gorilla on equipment. They are waaaay over built. The lone overhang makes mowing next to flowerbeds and trees really easy. The 425 has no trouble whatsoever handling this monster deck, even in very tall grass, and it cuts tall grass well. I only used regular blades on it, not high lift or gators. Even when mowing wet grass, this deck handles it very well, with little or no buildup, I was quite happy with this as my old 318 50" was horrible about wet grass. The only real item of mention is that when starting the blades, the engine better be warm or it'll stall, though once warm it starts with ease. The 60 handles rolling humps and bumps in the yard very well with almost no scalping, another great surprise.
The 54" is a different deck, very well made, but not a brute like the 60". I'd guess the 54 to weight 2/3 the weight, just not as much steel as the big bute. I tried gator (G5 I believe) and WOW! it almost made dust of clippings, so much so, you get a cloud of debri around you while mowing. All the screen intakes for the engine get covered almost immediately. Everything's a tradeoff, and if you can stand the dust, then they work like magic, clippings are well dispersed and fine. There is a spreader reinforcing bar that spans the bottom of the chute to stiffen the deck, which is good, and it doesn't affect discharge at all. This deck has to be the king of wet grass mowing, no buildup, and the deck looks polished in places it's so clean, absolutely fantastic. There is not much exciting about starting the blades, even when only a barley warm engine, cold it might stall, but not always, as with the big 60. With proper gage wheel setup, scalping in minimal, if not non existant, but it is not as easy to achieve as with the 60, which required no special setup. But, isn't that what gage wheel and roller are for? so no surprise they have to be adjusted.
If you can handle the weight, taking the deck on and off, and have a place to store the deck (assuming you don't keep it on the tractor), the 60 is the deck to have, without regard to your lawn. I'd keep the 60 even for a smallish lawn, it's that good.
My problem was, at 61, and in good condition, it was still hard for me to handle the 60 alone, and I don't store it one the tractor, so I opted to not go the back surgery route again, and traded for the 54. It's a great deck, just not the fantastic monster, commercial duty deck the 60 is, and I'm happy with it.
I read someone say, that the 60 was designed to mow every day all day for years and years without problems, and the 54 was designed for once or twice a week mowing, even of large properties, for years and years without problems, and I would totally agree.
Hope this helps the next guy looking for info on which deck to get or whether to keep one or the other. Truth is, these are some of the best decks every on Deere garden tractors, and I've had a few Deeres.