They are pretty much the same thing as far as performance goes, the 1080 being slightly stronger in some games, the 2070 slightly stronger in others, averaging out as almost equal. But thats with similar settings. The difference being DLSS which can be an advantage, and in DLSS2 equipped games can show a sizable advantage. There's only a couple of the DLSS2 games currently out, and whether or not that trend will continue to grow or nvidia scraps it in favor of something better or if game devs bother to include support for it is unknown. DX12 is supposedly multi-gpu based, not sli and thats still not really happened yet because of game devs lack of support in games.
There's also ray-tracing, which can make some games seriously more graphically appealing, minecraft is amazing with it enabled, but that comes at the cost of @ 100fps. So it may look stunning, especially for low fps required open world type games, but for the high fps demanding 1st person shooters, it's a flop. But it's an option the gtx series doesn't have.
So, older gtx as is, or newer rtx that has quality or performance boosts depending on the game. If they cost the same, 2070 no brainer is better, it has options. If the 2070 is considerably more then you must weigh the value to you personally as to if those options hold any value and is it worth the price difference.