No breathe now. I gotta stay calm and save for the Chamonix :p
To OP. May I ask why you are downsizing? Why not stay in 4X5? 4X5" cameras need not be big and heavy.
I just see 4x5 and MF as two completely different worlds (with the Fuji MF system that has movements being a strange & "wish I owned that" hybrid).
I just don't think you can "replace" one for the other; the process, gear, and results being markedly different.
Not saying "don't do it", just keep in mind that if downsizing is the deciding factor, be prepared for a very big change in how you make your art (or enjoy your hobby or produce your client work). My 4x5 gear all fits in one case (that hasn't been opened in a few years to be honest) so this doesn't have to be an "either-or" deal unless money is the major deciding factor. And even if budget is driving your decision, you could likely find a used RB, 645, Rollei or even a Kiev and shoot a few rolls to get a feel for the process & the results.
I'd vote for trying to have both systems available to you, at least for a while.
Everyone is talking about how LF cameras doesnt need to be bigger than MF ones, but the enlargers. Those are big, and you need even more space if you want to make big enlargements.
Søren: Woops! 2500 kr,- ;)
The Hasselblad and I get along really well. It's quick enough to set up that I can be responsive to quickly changing conditions, even react on intuition when I hand hold it. It's very easy and accurate to focus, and the lenses are superb. If you maintain your camera they are mechanically very good and reliable. It's a camera that really gels with how I photograph.
Good luck with your choice. I think only you can answer your question, since we're all different.
Thanks to all for the sound and thoughtful advice
If you can live without movements the hasselblad kit is a very versatile kit. But when you want movements, Only a camera with movements will do. Thats why i'm moving back into 4x5. The depth of field I want can only be done with a camera with movements.
Well, if you find you're missing movements, and you get into the Hasselblad system, there's always the Arcbody and the Flexbody to give you some degree (not nearly what you had with your 4x5, but still) of movement. They're not cheap, and they're not quite as straightforward as a 4x5, but they'll get you in the ballpark.
I'd suggest just putting away your LF gear for a while, and taking a break to see how you like being away from it. That way you won't regret it if you do want to keep at it. Plus, times change and you may find yourself wanting to go back later. Keeping what you can spare room for means fewer purchases and less money spent.
At least for me, working with my 4x5 film in the dark is relaxing, and it gives me an excuse to get away without leaving! :)