Matt, not so much the heft being what creates that momentum. 29″ wheels, ample tires and supple suspension keep me moving forward on rough climbs – despite the added weight. Bikes with a steep seat tube are very comfortable, efficient through the dropper stroke and climb exceptionally. Most modern suspension platforms are great performers up and down – they barely pedal-bob. So what, really, is the disadvantage of a true trail bike? A couple of pounds heavier, that I only notice when I lift my bike off the ground. Experience has shown me that I don’t have more fun on a less capable bike, and I value not feeling beat up after a long ride. If you like riding your bike, it will be less a chore to do it all day or days in a row.
Ride quality varies greatly between bikes, and deciding what is right for your present and desired riding after a long absence is a daunting task. Every ride on a different bike, even a parking lot ride, will tell you something. Keep digging into it, and be open to possibilities. Good luck zeroing in on something that works for you.