I bought the MX5100DT w. FEL recently. There are several reasons why I chose this tractor. It has the horsepower/PTO capacity that I may need in the future, it doesn't have a lot of electronics (less to go wrong), HST is nice, but I don't change speeds or direction often and everbody knows how to replace a clutch (as a mechanic pointed-out), the ergonomics were fine for me, and the price was acceptable. One thing to keep in mind is that you need to know what options you need now, or are likely to need in the future and what you plan to do with the tractor. Do you need draft control, various remotes, a mid-mount mower, or whatever. It may be cheaper to get what you need as a complete package (as in the Grand series), or add few or no options at all (to the MX). Does the tractor feel comfortable (seat, controls, steering wheel position, etc.)?
If I changed directions and/or speed often, HST would be very useful (and is available on the MX). If I needed more than one or two remotes...a different model tractor may have been cheaper than configuring the MX to that standard. If the MX had felt uncomfortable, I would have looked at a different model. Anyhow, that's some of the things I considered with the money I had available.