Between two hotels in Florence

I haven’t stayed in either but the location of Hotel Lungano is much better. The location of Regency is not good.

I haven't stayed in them either but would agree with Marco: Hotel Lungano is better positioned in relationship to many of the attractions you are likely planning to see. Looks like a lovely accommodation!

Both are known swanky hotels, but I would choose the Lungarno, which I know not because I stayed there but because my cousin lived next to it on the Arno. If you go in summer ask for a room facing the Arno. Besides the view it will amaze you the cooling effect that the Arno has on the rooms above it, compared to the rooms not facing the river.