When I set up a vocal session, I am most likely to put up a U87ai, an SM7b, and an AEA R84. Then, based on the singer, the song, and the mix role, I make selections and then switch up mikes for doubles or harmony parts.
The U87 and the SM7 aren't the same mic. Use them as part of a palette. If you're just starting and are on a budget, get the SM7 and another condenser (and a budget ribbon). Between those three mic styles and tones, you'll be able to cover a great deal.