I have three different opportunities at very similar price points:
1. Niche Zero for 700 bucks. New
2. Eureka Mignon Specialita for 500 bucks. A year old.
3 Fiorenzato F4 V1 for 400 bucks. Five years old.

The used ones are both in good shape.

I almost only do espresso. Very, very rarely pour over or French press and that's for guests who complain about "How Strong" my coffee is, so obviously brewing is not a factor for me!

There's also a Profitec t64 for probably 900-1000 but I'm pretty sure one of the three listed is going to get the job done.

So, which is the best bet?

Single dose grinder every time.

So you're sayin' the Niche?

Yes.

I've had umpteen flat and conical professional grinders over the years and the Niche is a doddle to make consistent, great espresso. And it's the quietest I've owned.

The Niche is also very easy to adjust and, importantly, get back to the same adjustment after a change. At this price point, the "flat vs. conical" debate doesn't hold much water for me when talking about classic, flat burrs. Even in the $2,000 range, there's a lot of debate, especially if you enjoy classic espresso.

Jeff wrote:The Niche is also very easy to adjust ... get back to the same adjustment after a change

I disagree slightly on both points. Compared to the near micron repeatability of a geared ring adjustment, the Niche is relatively coarse. Perhaps it's just me or my Niche, but the best repeatability is about 1/10th of an increment, there being 10 increments between numbers.

The repeatability is not an issue here as we normally consume the same coffee for a few weeks. If someone pops over with a roast, getting back to exact is a tiny PITA. But the upside is the new setting may be considerably better as happened recently. A tad coarser, ≈0.66 -> ≈0.75, 5s less brew and 2g less yield is a much better cup.

Note that these nits are picking the fly sh.t out of the pepper, but if you're round the bend like many here, something to consider.

FWIW, I've looked at pretty much every new grinder in the last 15+ years and the Niche was the first I bought in the last decade, before any had been made! You'll likely have to pry it from my cold, dead hands.