Tony, when I lost my Digisix (on a train, bummer) recently, I was confronted with either getting a new Digisix, or the Sekonic Twinmate. With the Twinmate, like you I was worried about a) flimsiness? and b) accuracy?
Why did I not run and just buy another Digisix?
It is very accurate, hard to kill (you drop it, it skips and laughs), smaller than the Twinmate, and handling is better than the Twinmate (Digisix: you can flip the dome from incident to reflected with the thumb easily.) Also the readout is instantaneous. (That is right, after a few weeks with the Digisix you have your aperture/shutter-settings in correspondence with EV internalized.)
But: for the money, it is not NICE. Tough, yeah. The scales are paint-on only and were not even painted crisply to begin with.
It shifts modes on you like nobody's business. Mine had BAD battery life. It will beep when it is inconvenient.
And you know what? It is still a great meter. But I could not get myself to buy another one (at the price it is going for), and the reason is: all these annoying quirks the Digisix has are design quirks that could easily and with little effort be fixed by the company with a minor redesign. In fact, the Digisix should never have hit the market with these flaws that are easily detectable in a short field test.
Now go read Dante Stellas review
http://www.dantestella.com/technical/digisix.html
Spot on. Written in 2002. Nothing's changed.
Gossen would have a REAL winner if they just cared to fix these small but annoying quirks.
So I got myself the Twinmate. I am more careful with it than with my Digisix. I does not come across as flimsy to me, but I doubt it would take drops as well as the Digisix.
The Digisix is probably a bit more accurate. But: I think the Twinmate is more than good enough for black and white work.
You say you are shooting Tri-X with a vintage camera. I think the one-third-of-a-stop readouts of the Digisix are overkill in this situation.
Now that I have owned both, I would again go for the Twinmate.
But: the day Gossen updates the Digisix, I would be tempted to buy it.
All the best, Ljós