Hello Kim.h, welcome to the forum.
There were two 1.7 CRDi engines, one was 114 bhp with a manual gearbox and a 1639kg kerb weight. The other was a 139 bhp with a DCT auto box which has a 1694kg kerb weight. Using the 85% rule that would limit the caravan to between 1394kg to 1439kg. So a lot depends on what you are towing.
I've not driven either car, both my Sportage's have been the 2.0 CRDi, but I suspect if you went for the 114 bhp you would have to work the gears to keep up a decent pace. The 139 bhp should be a capable engine, but I have no experience of towing with an auto box.
For the record, although you may not want to hear this, the 2.0 CRDi is a superb tow car. Good luck with your search.