I haven't done mech work for quite a while and I used Inventor mostly. From what I've seen of Bricscad, it is every bit (if not more) capable than Inventor.
Another reason to think about Bricscad is that it uses the .DWG drawing format as standard, this is pretty big as you can collaborate a lot easier without other disciplines needing to convert your drawings etc.
This would be my checklist for a 3D modelling package (regardless of discipline):
- Reasonably intuitive modelling (but not always necessary. For example, Tekla Structures is quite a different modelling tool but once learned was very productive compared to others)
- Must have the ability to produce quality 'live' 2D drawing views/sections/details from the model. Automatic detailing/dimensioning is a nice to have but I find I can spend more time cleaning drawings than just detailing myself. Inventor, Bricscad etc usually provide some level of automatic dim update features to make updates with changes.
- The ability to produce 'live' BOM's and other reports
Bricscad handles all the above well at a fraction of the price.
I'd definitely spend a few weeks learning and working with Bricscad (you get a month free trial), check out the videos that perform the listed points above to see how it ticks.