Yes personally I do prefer Urgyen Trinley Dorje.
But let us not go into debate on this matter.
As long as both practises well, has correct understanding of
Buddhadharma, attains realisation, they can be teachers.
'17th Karmapa' is just a role, one of the representations of
Tibetan Buddhism. And has a heavy task to spread Buddhism
especially in the future. Nevertheless I do hope this controversy
can be solved ASAP.