Most people, i.e. non-musicians, perceive music on a very visceral level. They either like it, they connect with it, or they don't. I think when people talk about "feel", or lack thereof, it is their attempt at giving a reason *why* they don't like it.
I get the impression MM sees this "sloppy" type of playing as undesirable and that while he possibly could play that way, he chooses not to. I wish he said it just like that, "listen guys, I know exactly what you are referring to, but it's not my style of play. Deal with it."
I agree with you, generally, Rumbo, but I don't think it is a matter of Mangini "choosing not to." I think it relates to his connection to the music he is playing.
Personally, I do get a more "clinical" vibe from Mangini's drumming style - as if he is slightly detached from the emotion of the song, and more focused on playing the parts. Whereas with Portnoy, probably because he helped shape the songs in some fashion (and in some cases wrote lyrics), always had a bit more emotion in his playing, and slight variance, because of his connection.
It's a very fine line to distinguish, and I think you sort of have to be a hardcore fan (like all of us here) to hear/feel it.
It doesn't mean Mangini isn't as good, or isn't capable of delivering that same "warmth" or emotional effect on what he plays, I just think he has been such a nomad over the years, and not very involved with the creation of the music, that he naturally just focuses on performance, not the connection emotionally to the song itself, if that makes sense.