I think you are comparing new versions while I'm talking about Mk I. (63 for Mk I, 65 for Mk III, 61 for Abrams, 54 for Leclerc, 62 for Leo II, according to Wiki). Merks are not that heavier when compared to others, though French tanks were historically light and fast and British heavy and slow. Still, Merk is comparable to others but as I said, Mk Is had weak engines and were underpowered and not overweight with regular engines. Granted results may be simialr but it's easier to put in stronger engine than reove weight.
Wiki lists higher speeds for Merks, though I guess it's again question of which version and what loads we are talking about.
My '97 Janes was giving data for Mk 1 Merkava and M-1 tanks (105mm gun) Abrams. My other, more recent tanks books give heavier weights as well I'm sure the current models are much heavier.
Interesting question is whether Merks made after the '67 War will be more or less underpowered than OTL Mk 1s.