The 5.5-ton for lot-line digging in town.

The U55-5 reaches about 11'11" deep, close to a full 12 feet, which handles deep foundations, drainage, and full basement work.
They're nearly identical in weight and power, but the U55-5 has tight tail swing and the KX057-5 is conventional. If you're digging in town, close to sidewalks, neighbouring lots, or existing structures, the tight tail swing on the U55-5 is the reason to choose it.
It weighs about 12,250 lb, which puts it in dedicated equipment trailer territory with a heavy-duty tow vehicle. I'd confirm the exact trailer and truck rating with you before finalizing a purchase.
Yes, a cab is available at this size, which most full-time operators choose for weather protection and comfort over a full season of Grey-Bruce work.
This is a full-time working machine for excavation and municipal contractors doing regular in-town digging where clearance around structures matters. If you have open working space and don't need the tight-tail advantage, the KX057-5 covers similar ground.
Tell me about your property and the work you need done — I'll point you to the right machine, even if it isn't this one.
Tell me what you're working with