I have both PhD and DClinPsy, and held several academic posts during my career (No PGCE). I have balanced usually an NHS clinical post with a university academic post, or have had a clinical job with a strong research link somewhere.
Broadly, you can get university lecturing positions with either, but there are subtle differences in the posts you could get. You can 'guest' lecture with either. With a DClinpsy you are in a good position toto get a post on a DClinPsy course as a clinical, academic or research tutor. As a DClinPsy is a very specific practitioner doctorate, its a good platform for working in such a department -although your focus is more likely to be on getting trainees through training, as this is what you will be primarily hired for. You are also eligible for certain post doc, research therapist and other allied university roles with a DClinPsy. It is a really versatile qualification, but IMO it's possibly less helpful if you want to go down a pure research route, and I have had a few colleagues who have struggled to make the jump to professor level with just a practitoner doctorate.
A PhD is usually a pre-requisite for a research intensive university career, and moving towards becoming a primary investigator, winning your own grants, and going up the academic chain. In fact, the MRC and other bodies offer a post DClinPsy PhD route (a fellowship) to do this but this is usually much rarer for Clinical psychologists, as the vast majority end up working in purely clinical NHS posts. Many will have done a PhD before getting onto a DClinPsy, as it is excellent preparation for clinical training and is the route I took . On the downside, a PhD by itself doesn't allow you to do any clinical work and lacks the breadth you get with a DClinPsy.
Hope that helps, as I am aware there is a major lack of information around this in the public domain.