Ideal inductors and capacitors are lossless (by definition).
Real ones are not, and additionally have nonideal reactive
elements (ESL for capacitors along with the straight-loss
ESR; interwinding capacitance, leakage inductance and
series resistance for inductors.
The "less sensitive to variation" is a mystery because
otherwise component values wouldn't matter. Maybe this
is a simpleminded observation that f=1/sqrt(L*C) so the
resonant frequency has a square-root rather than linear
dependence on either one.
But an LC tank is certainly more sensitive to inductor
variation than it is to resistance variations, which it has
none of (besides the parasitics).