Love the look of the Genisis range at the minute...
They seem to have got it right IMHO.

Genesis would be my choice personally.

Cannondale is stepping up their game. Might be worth a look?

I've been riding a fortitude ss for last 6 months. Honestly reckon it's the best bike I've ridden.

Swapped the bars for Atherton Pro's and switched the chainset to XT.

Genesis Fortitude.

I've had a Fortitude SS for a while to - it's fine for what it is but just be aware you can't fit suspension forks later if you end up wanting a bit more versatility. I bought mine for short rides on local non-techy trails and it's great for that but even then I end up with sore wrists after about an hour and a half. I rode it down a rocky trail in the Mendips once and I couldn't see where I was going at one point due to my vision blurring from the rattling, fun once but not something I'd want to do again. It's certainly far from the best bike I've ever ridden and is a complete rip-off for the spec.
If the Unit can take suspension forks and you think you might want to ride it on long days/techy stuff in future then I'd say look at that instead.

Kona unit. Has a high stand over height, so if if it fit's you it;s amazing, as a single speed. Ut will take 100mm suspension forks, even longer most probably. You can add gears, though weight wise, i think it's best as a single speed, being nicely balanced. All the stock parts are great, consider a wheel upgrade later on, especially if you want to run gears as the included set are single speed only.

Seriously it's very good and looks even better in the flesh.