The summilux 75 is a large lens, but it is much lighter and smaller than most SLR kit lens, especially from the slr lens made in Japan era.
I walk around with mine everywhere, and have used it with out strap for all day use at events.
The Summicrons are great lens, but they don't have custom made glass like the Noctilux. The lux also focus close - 0.75m is close enough for anything I've ever needed, and closer than both my 35, and 50 luxes.
The lux is a fine lens, and if you like to take fine art photos, this is the lens you should get.
The cron is just a lens. If you just take photos, then the cron might be fine 😉