My only Twsbi is an Eco, I haven't tried their Vac filler models. Once I had tried the v126 I couldn't look at a $70 Twsbi the same way, even though I like the Eco.
I've looked at the Nahvalur pens, really like the Nautilus, just haven't wanted to pull out the wallet for it. (I'm looking at Pelikan and Conway Stewart for some bigger purchases.)