It depends on what you’re after. The Royal is one of the more ‘modern’ sounding SPU’s, using an advanced stylus profile (Gyger Replicant 100). If you want to pursue this modern sound (in terms of detail retrieval, soundstaging, etc.) the Royal is probably your best bet in the current lineup. Perhaps the 100th Anniversary SPU (with Shibata tip) goes beyond this, but I haven’t heard it.
You have to be aware there are also folks who are devoted to the ‘old’ SPU sound, represented by the SPU Classic in the current line-up. This has a spherical tip that limits frequently range and detail retrieval, but offers a sonic presentation that some people adore.
Most of the other SPU’s are somewhere between this old (Classic) and modern (Royal) approach, using an elliptical stylus and different coil wires and suspension designs. In my opinion the earlier Anniversary models (A85, A90 and A95) offer the best of both these worlds. They were limited series and are long deleted, so only available on the used market. This obviously has a certain risk, but Ortofon does offer complete rebuilds for these models, at a price.