Hi. I spent weeks agonising over whether to get Toby an Equafleece or an overall "raincoat". I decided on an Equafleece which he has been wearing for two weeks now. He loves it and it gives him more freedom of movement as well. Toby wears it while he's out as it keeps him warm and all the covered bits of his body are bone dry when I take it off. It's really only his ears, feet and inside back legs that get wet. I wouldn't be without it and OH has just bought him another one for Christmas - just waiting for it to arrive. If you go with an Equafleece, I don't think you'll need the slim fit - just measure from breastbone to base of tail. Toby is 22" and it fits beautifully.
PS so easy to wash and dry as well. I just put it in the airing cupboard and it's dry in an hour or so.