The paper side of the modelers is definitely a weak point. The latest release (R8) of inventor allows you to model in Inventor and detail in Autocad, while keeping the link in tact. (change model and dwg will change) Right now it only works with part files and not assemblies, but will probably come in next release. I don't use this feature very much, so I can not vouch for the stability.
The other issue with the assemblies in Autocad from Inventor would be all the intelligent data from the model (parts lists, auto balloning, weight, and other custom properties that you could currently carry into the drawing from the model)
This topic has been discussed at great lengths in many places. It is a hard decision (but you have to do it or get eaten by the competion)
You can get evaluation copies from the software people and do an eval of your own. You also need to get them to do a demo (and have them use parts like you would use, not the scripted demos they have). Give them an autocad file of a tough part to model and see how it works. I am an Inventor user that recently test drove solidworks for 6 weeks (and went back) Make sure everyone you are talking to is using the latest of each (solidworks 2004, or Inventor R8). Both have some new stuff and it would not be a fair comparison.
Pricewise, with Inventor you get the latest Autocad mechanical (2004DX) and the latest Mech Desktop with the package. The price will be very attractive until Jan 1 (when you can no longer buy an upgrade from Acad 2000 and you will need to get a NEW seat). I'm not 100% positive about the Jan 1 upgrade date, so talk to your reseller.
You can read the comparison at great length on many different sites (and the CAD magazines too). Just do some searching.
Good luck