I love my G-tech for a quick flit around, but it doesn't deep clean.
For giving the carpets a thorough cleaning, I have a SEBO Automatic X7 Pet ePower.
It's a heavy bugger, but has extension tube and accessories 'on board', including the stair and upholstery turbo brush, which is wonderful for cat hairs!
It also has a very useful headlight so I can spot the muck easily
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If it's going to be the cleaner dragging it around rather than you, I'd say definitely go for one! John Lewis have them on at £399.90, I usd my JL credit card, paid it off immediately, and got double points due to an offer, win win!