24-70 f2.8 vs 24-105 f4

Currently on a cannon 60D but Im hoping to move to an R8 in the next few years. Id like to buy a quality zoom lens that I can use on my 60D now and later adapt to the R8.
Trying to decide between

Tamron 24-70 f2.8 G2

Sigma 24-105 f4

I like the longer focal range and lower price of the sigma, but Im worried about the slower aperture as I like to shoot at dawn and dusk

I like to shoot landscapes, animals, cars and architecture plus a bit of portrait