Horses for courses.
Russets where a dry potato is needed -- as a straight baker, but especially for potato galette and pancakes. I loves me some latkes.
Waxy potatoes, like Alberts for salads.
New red potatoes for boiling and tossing with butter and parsley. Also good to saute for O'Brien.
White potatoes for tournee and pommes saute. I like the way they brown.
Yukon Golds are good mashers -- especially mixed with a little parsnip. I think a lot of "diet conscious people" (aka women) like them because thy look like they have butter in them. Don't be fooled. They need as much butter as anything else. Plus, you've got to watch Golds. They're a little watery for some uses, also they have a tendency to break apart the second they're the slightest overcooked.
Colored fingerlings -- purple, e.g., to side with light colored proteins like fish and chicken.
And so it goes.
For the lightest, fluffiest mashed potatoes, rice the potatoes instead of mashing. No matter how you mash, work the potatoes as little as possible. Overworked potatoes are gummy -- and it's the world's most common screw-up. You can incorporate the butter and milk separately. But whether separately or together they have to be tempered before incorporating. You can put them in the pan cold with the hot potatoes, give them half a stir and let them sit over a low flame until the butter has a good start on melting, and then stir them in. Be gentle, darling. Twice as much butter as is healthy is a good start. They should be a touch looser in the pot than you think they need. They'll stiffen up a little on the plate or in the bowl. I know you're not going to forget the salt, but don't forget the pepper either. Potatoes love a little pepper (corn too!).
Rich