My husband and I stayed at the Palazzo Guadagni on both of our visits to Florence, in October 2018 and again last June. We really loved the hotel - it's in a historic building with a lovely outdoor terrace and beautiful rooms. We loved the high frescoed ceilings and found the rooms to be very spacious compared to Rome, though I can't compare to other rooms in Florence. The furnishings definitely feel antique, so not new or modern, but we liked the atmosphere.
On our first visit, we stayed in a room with a balcony overlooking Santo Spirito Square. There are cafes below and it was very lively at night, though we are night owls so the noise didn't bother us, and closing the windows shut out a fair amount of noise.
On our second visit, we stayed in a room next to the entry desk. We were conscious of a fair amount of noise outside but again it didn't really bother us. Our room had a double set of doors that muted the sound quite well. And we were there during a very hot week in June and were extremely impressed with the efficiency and coolness of the A/C... we had low expectations for how good the A/C would be and were very pleasantly surprised. (I'm not sure when they will turn it on in the spring, so I suppose it's possible you might not have A/C for your visit.)
Florence is very walkable so we liked being in the Oltrarno and walked many places we went (also the hotel will call you a taxi as needed). If you choose to stay there, there's a fantastic gelato place right around the corner: Gelateria Artigianale La Sorbettiera at Via Mazzetta 9/a (currently Google says they're temporarily closed; maybe that's a seasonal location). Some days we went there twice a day. The flavors change throughout the day as they sell out.
This ended up being a lot longer than I planned. Hope it's helpful and enjoy your trip!
