3x EVGA 980ti hdyro or 3x 1070 FE?

The EVGA 980ti Hydro is very “cheap” at the moment.
Would you recommend 3x 980ti with the AIO-cooler or rather 3x 1070 Founder Editions with the blower fan? The 3x980ti s would be a little bit cheaper.

And it is a problem to mix different generations of GPUs? Like 900er series with 1000series? Are there any driver conflicts?

3x 1070 2GB more VRAM. You can combine most genarations. I use GTX 770 and GTX 1080.

@MZGarmi : Thanks a lot for your reply.