Yep, and to continue the discussion.... less is more in terms of speed. Shorter travel, generally, with aggressive geometry means a tauter ride. It all depends on what you intend to ride it over. If you are on local trails and bridleways you're not going to be doing huge tabletops and chutes, and in reality not so much of the rocky stuff. A taut XC bike like the Titus X or the 100mm travel Spesh we linked to above, will be fast, and possibly furious. I ride my XC hardtail over some local trails back to back with the 140 bike. There's no doubt at all which is better for climbing, and the hardtail is every bit as efficient if not more so on smooth pedally stuff. Hit technical descents, or really rocky stuff though and I can just plug my way through them on the longer travel. Hit a rocky descent on the HT and it all gets lairy and nervous . A 120 mm bike may well fit the compromise gap between the two, but it won't give you the bottomless travel of a 150 or even 160. 100mm FS XC bikes tend to benefit from improved grip at the back wheel, but not the sort of squish a 15 stoner needs to go down a set of rock steps day in day out! Lighter wheel and tyre options will mean more pinchflats and rim damage so
I'd be tempted to say get a 120 rather than a 140 if only because the 140 can feel a bit wallowy on smooth stuff (although setting rear preload/sag and using propedal more selectively will mean you can tune to what you ride) You mention your weight, which, like me, means more travel will be better for comfort, but the compromise is more to lug on those day long epics. For that reason we can avoid the playbikes like IBIS and Yeti etc. Your riding simply doesn't need all that travel.
That said, the Canyon 150 bikes are light, so your epic long rides are back on the table. You can tune preload and travel to suit the terrain you ride on, and if necessary tighten it all up. I know some riders with RP2 XV shocks that never turn propedal off.... simply because it's more efficient on everything they ride, but then they never expect to hit big drops or jumps.
I've managed to argue myself round in a circle, and am edging towards the Canyon AM once again. Well tuned and in more or less standard trim it'll winch a big guy round pretty much everything, you won't necessarily be overbiked, but if you do decide to edge towards trail monkeyhood, you won't ever be underbiked either!