Unfortunately, fatal errors are not just caused by the MDT software. They're usually related more to the interaction with Windows and the way that Windows handles memory. You won't avoid the fatal errors by switching to a different program. A better approach for that is to double check that you have the latest video drivers (and the correct ones) for your video card, and thet the setup of the drivers is correct. It also helps (at least with Solid Edge) to have static virtual memory instead of the default dynamically-allocated virtual memory. Set it to at least 2x your installed RAM. That should at least mimimize the amount of fatal errors. Also, save your work a lot.
I have been using Solid Edge steadily for about 4 years now. Before that I used AutoCAD for about 14 years. The difference between the two (and MDT is similar to AutoCAD) is amazing. Solid Edge is very strong in sheet metal, and from what I've seen in demos is the best of the three (although I'm sure others will disagree). My main complaint is that I use the mouse a LOT more with Solid Edge, which led to some wrist problems until I switched to a trackball. No commandline to type in shortcuts.
As for which would be best for you...
1. Do you have legacy work you need to convert? If so, check that very carefully. The three programs are not very good yet at translating work from one to the other and maintaining the feature structure. Probably going from MDT to Inventor (since both are AutoDESK) would be the least painful where this is concerned.
2. Do you do a lot of assembly work? Solid Edge's main weakness is in that area as far as I'm concerned. Solid Works is probably a little better. Inventor I don't know about.
3. Do you have access to local expert advice (friends, co-workers, neighbours, user groups) in any of these programs? Once you choose one of them this local expert advice may become invaluable to you to getting up to speed. On-line help is also very useful but there's usually a delay between question and answer. Getting the answer right away will help a lot.
Hope this helps and good luck.