If you want to see everything... then you'll need a bigger scope
The SW 120 apo should more or less match a small SCT (6") for detail, but not the larger ones. Light grasp is important for planetary too.
For nebulae, clusters, galaxies... it's aperture that counts. A larger reflector (SCT, newt, Dob...) will win practically every time unless the subject is particularly large such that it won't fit into the field of view of the larger scopes.
The contrast situation of SCTs is often overhyped as all the surfaces these days are coated for good light transmission and the secondary obstruction only reduces the contrast by the proportional amount of aperture. If you could compare a 10" SCT to a 10" refractor, you might see some difference, on a good night
what you see with a large scope, at least at higher magnifications is affected by how good the atmospheric conditions are.
If you want better contrast, prepare to empty your pockets for either a large apo or large Mak and a more expensive mount
Many people here have more than one scope because any single design doesn't excel at everything. It's just a question of picking the scope that matches your priorities the best. You might find that a solution that includes a smaller portable grab-and-go scope and a larger aperture beast works well.