Richard J.:
I've found some dimensions to compare. These are overall train widths
in metres, London figures from Tubeprune's site, Paris from Alstom's
site:

London sub-surface: A (Met) 2.95; C (Circle etc.) 2.92; D (District)
2.85.

London tube: 67/72 (Vic, Bakerloo) 2.64; 73/95/96 (Picc, Northern,
Jubilee) 2.63 (Alstom's site says 2.6); 92 (Central, W&C) 2.62.

Paris: MP89 (Lines 1, 14) 2.45.

MP89 look at least as wide as the earlier Paris types. So, rather
surprisingly, Métro stock is actually narrower than all London stock
including the small tube trains.

But remember, there are places in a tube train where the ceiling is
too low for most people to stand. A simple width measure doesn't
provide a complete comparison.

(For that matter, it would also be informative to compare train
lengths. Paris trains are relatively short, I think, but I don't
have numbers handy.)
--
Mark Brader, Toronto "WARNING: Pastry may be *hot* when heated."
-- [alleged] Kellogg Pop-Tarts box

My text in this article is in the public domain.