I have driven all three cars. I'd go with the Ioniq. The Leaf is cheap, but dated. No technology. The 2017 e-Golf is a great car, but has an excessively high price tag. The Ioniq however, is both a great car and very reasonably priced.
Electric cars are bad for second-hand value anyhow. These days, the e-Golf thas such a high original price that I think it is bound to lose very much value in its first years. Probably wouldn't be so bad if it had been more reasonably priced from the retailers.
You should also consider Opel Ampera-e. It has a great range, which will surely count a lot when selling it one day.
Electric cars are bad for second-hand value anyhow. These days, the e-Golf thas such a high original price that I think it is bound to lose very much value in its first years. Probably wouldn't be so bad if it had been more reasonably priced from the retailers.
You should also consider Opel Ampera-e. It has a great range, which will surely count a lot when selling it one day.