I don't have both. And since the
L4400 was at the top of my budget I didn't even research the MX5000 much. So all I can tell you is what I think of the
L4400 from a few days of experience and what I can read about the 5000. In regard to the 5000 it looks like you get a bit more HP, a stronger hydraulic pump, more loader options (and I suspect a more powerful loader). I can't tell what difference there is between the trannies. The 5000 doesn't seem to have a GST or HST but it is a synchro....so I assume you can do some shifting on the move, which is nice. I'm guessing, but don't know, that the 5000 is a more robust tractor. It sounds like you get about $1500 more tractor for your $1500. If it had been in my budget I definitely would have given the 5000 a serious look.
Having said that, I'm very pleased with the 4400. You may have read some of my earlier posts. It has truly exceeded my expectations. The loader is very capable and I've done some significant road repair in very difficult soil (rocky, dense clay) with it. But the best example is probably its performance with a 7' mower. Simply flawless in deep grass and brush. It did not tax the motor at all. I've been surprised at the available power in this little tractor.
I'd let your budget be your guide. If $1500 isn't a hurdle then I think it is an easy decision to go with the 5000. If it is a stretch then I think you can get the
L4400 without second guessing what might have been. Also consider what attachments you can get with the $1500 you save on the
L4400 as well as the fact that the loaders for the 5000 will likely increase its cost as well. Good luck and let us know what you get.