I haven't used SolidEdge, so I can't comment about it.
SolidWorks uses a linear part feature tree and has to step its way through each feature in turn. An analogy here is if you were modelling a large assembly and you put all the components in at the top level (i.e. no sub-assemblies) it would perform slowly.
Some other CAD systems (eg. I-DEAS and I presume NX since they are being merged) can use what are referred to as "bushy" trees, which offers a great deal of power and flexibility. Features can be grouped into sub-branches that are evaluated independently e.g. all the features to make a complex rib can be grouped together, and you can roll back the history to the top of this group so that you see just the rib on its own.
Whole branches can be associatively copied around the part (as well as patterned of course) as well as to other parts. In I-DEAS, it is also possible to "save" the data in each branch, which stores the geometry resulting from evaluating the branch so that a rebuild further down the tree does not require the branch to rebuild.
If you decide that one complex rib style is not best-suited to the design, you can substitute another one (from a library for example) and swap out the branch whilst maintaing associativity (using surface mapping) to the original surfaces/planes etc.
Further performance emprovements are:-
- you can "lock" the history tree so it does not evaluate any features below a certain point (unless they have changed).
- you can evaluate each feature without evaluating the complete part. So if you want to change the dimensions in various features you can see the effect on those feature without needing a full rebuild.
- you can turn off automatic updates, so the part (or assembly) only updates when you tell it to.
So the long answer is.....other systems do it better. I-DEAS is probably still available in "Artisan" form for £3800 (pounds). If you need advanced surfacing, that's an expensive option. There is a free license transfer to NX.
Of course, there are many other things that SWX does better too......
Regards, John H