I think the best advice is to try both. As everyone has already mentioned, topre is it's own beast. If you are able to afford it, but a nice topre board. That way if you don't like it you will have an easier time selling it afterward. Not to say you wouldn't with a Novatouch, but if you are gonna spend the money, might as well get a premium board. I have a HHKB and a RF87UB-55, and I will be swapping my HHKB to 55g very soon. The added weight isn't for everyone though, as has bee said. Keyboards are very personal, and you honestly just need to hop in and see which switch you like most.
You seem to imply that the Novatouch is not a premium board, and that the HHKB is.
I hope that by premium you don't just mean "more expensive".
A silent modded Novatouch is definitely a class above the HHKB, even a Type-S (I own both the Novatouch, which I have modded, and the HHKB Type-S). It's a class above in quality, and it's way less expensive.
I understand some people like the HHKB layout, and I'm fine with it (except that I find the layout horrible - maybe it's just me).
A modded Novatouch has both a very classy sound and a superior build. The HHKB has no metal plate, it's just a hollow plastic case, and you can feel it and hear it with every key press.
Now this has its advantages. Clearly, the HHKB has a smaller footprint and is lighter, which is great for mobility.
However I find the HHKB to be an extremely overpriced keyboard that does not provide the build quality that should come with the price. If you really want this layout without arrows, then I guess it's OK, otherwise it's a waste of money.
For a desktop and serious productivity, the modded Novatouch is the premium board of the two. I would agree that the stock keycaps are weak, but at least you can use Cherry MX compatible keycaps on it, so it's easy to find better ones.
Regarding the OP's question, it's really hard to tell.
Personally I love both the Cherry MX keyboards (reds or browns) and the Topre ones. I don't want to choose one over the other. After using a Topre board for a while, it's always a pleasure to re-discover a Cherry MX keyboard.