[Tristan Lall]

Ian and I had a portion of this discussion a few days ago. At that point, I was recalling vague rememberances of the good and bad things in both packages. But just this past week, I was using SolidWorks (2005 SP5), and remembered just why I prefer SolidWorks over Inventor, but still don't love either.

One caveat; maybe this has all been improved in the latest versions. It's expensive, even for a business, to have the latest versions of these packages, so I'm necessarily and perpetually behind the times.

In essence, it comes down to the features. Inventor ships with the basic sketch-and-model capabilities, but like Ian said, the parametric options aren't the best, and trying to program mathematical relations between assembly members isn't very well supported. SolidWorks, on the other hand, has much better support for these things. In fact, SolidWorks also supports more advanced feature creation than Inventor, and uses a more straightforward interface to accomplish it. The left-side menu has the options conveniently arrayed, while Inventor throws up dialogue boxes* which are inconsistent in form, and often don't clearly express what's going on.

SolidWorks also does a better job in the sketcher with guessing constraints, and adding them. I hate the way that Inventor won't make most things constrained, unless you force it to (several mouse clicks later). I still prefer Pro/ENGINEER 2001's sketcher, though; despite it being a huge resource hog, it guesses geometry and adds weak constraints and dimensions, which are enough to fully constrain the sketch. Actually, I don't like the way that Inventor and SolidWorks don't insist upon fully constrained and dimensioned features—being a bit of a pedant, I'm constantly annoyed with CAD models which allow parts and features to float around, unconstrained. (Unless, of course, it's a motion analysis.)

Inventor's sheetmetal mode annoys me, though. It's awful. When working on the design for 188's most recent robot, we tried briefly to do it in Inventor (because that's what the people with whom I was working knew best). The trouble was, even when using perfectly correct bends, with reasonable radii, reasonable stock thickness and only a few internal cutouts, Inventor refused to generate a flat pattern that was suitable for laser cutting. Chunks were missing. That's totally unacceptable in a design package, since from a manufacturing perspective, a geometrically accurate flat pattern is absolutely vital to actually making the part. Pro/E 2001 had no problems whatsoever with doing the same thing; we used that instead.

When you have to CAD things as part of your day job, you get to appreciate the little things in the interface which make it run smoothly. In fact, my biggest objection to SolidWorks isn't a big deal functionally, but it's a persistent annoyance: when using the "Add/Edit Mates" function, there's seemingly no logic to the way it uses the "Confirm" button (i.e. the checkmark); sometimes, when you confirm an edit to a valid mate, it keeps you editing the same mate, until you hit "Cancel" (the X). (That means that "Confirm" really means "Apply".) Other times, like when creating a mate from scratch, "Confirm" means "OK", because it moves onto the next mate. But these behaviours are both inconsistent with the usual "Confirm" behaviour—which is "OK" to the entire mode, not just the one selection (so you would go back to the main part or assembly tree). It's confusing, and non-intuitive.

Actually, despite its quirks and its own grevious UI problems, I still like Pro/E 2001 for modelling and assemblies. It's powerful, and what I'm used to. But I've got to try Pro/E Wildfire 3, eventually.

For drawings, though, anything but Pro/E 2001 suits me fine! (Without Pro/DETAIL, Pro/E 2001 is distressingly bad in drafting mode. It takes at least twice as long to do the same things as Inventor or SolidWorks—in terms of time consumed, it's no better than AutoCAD, in fact, despite the fact that the geometry is already there for you!)

The bottom line here is that SolidWorks and Inventor aren't nearly on the same level as CATIA or Unigraphics, in terms of their applicability to industry. SolidWorks (properly optioned out) is challenging a standard copy of Pro/E more and more these days, but then again, Pro/E, with the more expensive options, challenges UG and CATIA. Inventor just simply doesn't have the advanced capabilities of any of these things, or possesses them at a vastly inferior level (e.g. mechanical FEA, thermal FEA, kinematic/dynamic analysis, straight-to-NC-machining output, PDM, data conversion, etc.). It's a lightweight package, and is correspondingly unpopular in the engineering industry, except in sectors where low cost is the only requirement. Look for it to gain acceptance in the design of fixturing and equipment (which are relatively simple), before it progresses (several revisions from now) to parts with complex geometry and large assemblies.

Basically, if you have the choice of SolidWorks or Inventor, choose SolidWorks. But give a basic edition of Pro/E a look, if it's within budget (and if Wildfire 3 turns out alright...which, judging by recent history is no certainty).

*Modal ones! Of all the stupid things they could to to the UI, modal dialogues—where you can't shift the focus to another window—are right up there.