I do not think I would ever mistake any recording I have heard on either label for the other. Apples/oranges. I associate Telarc with mostly digitally mastered recordings whereas MLP in their day was 100% analog (with later masterings in the 90s to these CDs).
Fascinating how such different beasts can still both sound very good.
Analog warmth, soundstage and dynamics are the hallmarks of the best MLP recordings. I do not necessarily consider these to be more strictly natural sounding in timbre, but most enjoyable and involving regardless.
MLP recordings sound very good on my OHMs in particular due to the simple miking techniques used in most/many. The soundstage is absolute top notch in regards to size and positioning of instruments within and that allows a lot of natural detail and a high degree of musical involvement. In this regard, I would say the closest sounding modern recordings I know of are those on the Mapleshade label, which employs similar production values in regards to how performances are miked. Still I doubt I would confuse a Mapleshade with a MLP recording. Two different beasts from two different eras still.