Depends what type of objects you want to image.
Very short focal length like a lens is great for widefield vistas and some large extended nebulas will be great but still generally small on a DSLR chip.
Short focal length like an ED80 (especially with an (almost mandatory focal reducer/field flattener) is great for Orion, Tarantula, Eta and other large nebulas, but ultimately disappointing on galaxies and planetaries and some globular clusters and open clusters - just because they end up being quite small on the DSLR chip.
Long focal length (like a 8-10" newt or SCT) are great for getting in close on galaxies and planetary nebulas, globs etc, but place greater demand on guiding and you just can't get a widefield view if you wanted it.
Check my
Deep Space Gallery pages to see how Deep Space objects look on an image using an ED80 with 0.8x WO field flattener/reducer (with the exception of the widefield category, where they were taken with a camera and lens piggybacked - not through the ED80).