Navis imop is by far the best tool to use for clash detections. We have upgraded one of our premium to ultimate specifically for this (and a little inventor on the side). I really don' think there is much else out there that does it as well with all the different file types as does Navis.

To answer the question directly, Navisworks Manage.

As for whether Manage is worth the upgrade price from Simulate for clash detection alone? That's a how-long-is-a-piece-of-string question, clearly, but if you've found the Revit interference checker cumbersome, and are working with data sets to large to complete manually, there's good argument already.

I find the report generation function of particular use - I'm not keen on the thumbnails (they're more often than not nothing short of useless) but the element ID is handy for your operators to locate items to fix them - but it beats running around a Revit model with the snippy tool and a blank word document that's for sure.

Depends on the types of clashes you want.
If it's purely Geometry, NW is the best imho.
If you want to extend this to a rule-based clash, for instance: does my design meet all owner's requirements, does this doorswing interfere with anything, you might want to try Solibri Model Checker.

Caveat for solibri: it works with IFC only. And the Revit -> IFC process can be cumbersome and faulty.

I think I've seen a method of modelling swings with "invisble" nested families that reflect a panel's swing extents, which if set to show/export - will report a geometry clash in NW. I think. Not tried it mind.

I know.. CAN be done... but it's not NW's strongest selling point. For these kind of thing, Solibri has way more tools (although not easy to set up, when you're done it works great)

Navisworks Manage is spectacular, but it means asking some really brutal and hard questions:

1. Are you looking for lightweight interference detection for "design intent" purposes, or are you looking to tell the owner you have a "completely buildable design" that can be installed with no issues in the field? The latter is what a lot of firms market, but they are really doing the former, and there are some interesting reasons why:

1a. Whos models are you clashing? Design Engineers? Or subs? Im assuming Engineers and Architects, since were talking about the Revit Clash reporter. Thats all good and well, but a mechanical fabrication/installation model can vary wildly from the Design Intent model, especially if there is no contractual stipuation on the engineer and the fabricator to put things in cohesive spots. It can make Clash Detection worthless. Plus, a lot of engineers shy away from some of the fab LOD necessary for the real project, and gusset plates and misc. metals can be the deal breaker in collision detection.

2. Whos running it, and whats the clash process?

2a. Manage is amazing. But, its not like you plop out all fo the disciplines, and then read through an automated clash report, and youre done. There has to be priority, there has to be hierarchy, you have to have an order, and a process. And if you dont have this... The process is mostly for show. And if you DO have it, done correctly its a ton of work.

3. Who is doing the installations in the field? Its all good and well if you have a clash free model, but that doesnt do squat if the Fire Sprinkler guy gets in there early and uses everyones space. If you are going to take the time to clash detect, the owner needs to understand its meaningless unless things are installed EXACTLY as they are in the models. Is the GC/Subs using the models for layout? Do they even know what the model is? If they arent, then sure... Weve provided another level of coordination in Design, but it wont see full fruition.

Manage is a great piece of software, to be sure. (The limitations discussed about rule checking are true, but its great for collision detection). But the software currently isnt the weak link in the process. So have a serious conversation with your office about the potential for ROI with it, because its not like "you buy it and suddenly we can do it."

It took me about two weeks to create my first clash reports and prepare to present the results to our design team and client.
Using Navisworks & Powerpoint.

I think I know the answer (formatting) but I'm going to ask; why the fuss with the powerpoint and not simply use the OOTB report?