The blades are all on par with each other, IMO, so for me it would come down to handle ergos and sheath.
If you don't intend to get a custom sheath, then some of the newer offerings are better in that regard. The LMF collaboration, marketed as the Swedish Fire Knife, got pretty high marks for its sheath, as did, I think, the new Robust model. The sheaths on the Companion models, the new Allround, and the Bushcraft series are all decent by Mora standards, too.
As far as handle ergos go, that's pretty personal. Ragweed Forge* does have notes on each model as to what size hands they are best suited for. I have medium/large hands with somewhat short fingers, and the Allround (same basic handle design as the Companions) is a little smallish, though with the arched top of the handle, it fills in the pocket of my hand pretty well, so it's not bad. The Robust seems more hand-filling, and likely better for prolonged use. The Bushcraft series handles have a nice feel, a bit more hand-filling for me than the Allround/Companion grip, and the material has some give to it. Pretty comfortable. Overall, you probably can't go wrong here, though. It's more a matter of "I like this one better" than "this is unusable" when comparing Mora handles, as they all seem decently designed.
Here's a pic of the Topq Allround, which is the Mora I currently own:
http://www.moraofsweden.se/5.0.0.0/78/files/download.php?file=../../../20.0.0.0/911/9d30db8cdc460c10868025e400add1bc.jpg
I went with it over the Companions just for the slightly thicker/longer blade. Sheath may be a hair better, and the spine finish is a bit better (though not terribly important).
*Note: I'm not endorsing Ragweed, as I've never ordered from them (but plan to). Just giving it as a reference for the info provided on the site.