Camera
With the One M8, HTC focused on image quality rather than megapixel count, but this year it's slapped a heavy-duty 20MP snapper around the back of the One M9. Last year's 4MP UltraPixel lens appears around the front.
Samsung doesn't quite match that spec, but our early tests show that the optimised 16MP snapper of the Galaxy S6 is far superior than HTC's Sony-powered effort - although HTC assures us an improvement is coming there.
The inclusion of optical image stabilisation technology should help minimise camera shake, plus the new Pro mode added to the camera software is likely to make for an improvement in quality too.
Not much to separate the two flagships in terms of specs then, but it looks like the Samsung Galaxy S6 has just edged it in practice.
Battery
The size of a smartphone's battery isn't the be all and end all as far as battery life goes, but it certainly helps. The HTC One M9 sports a 2,800mAh battery, which is a step up from the 2,600mAh cell inside the One M8. Last year's model did pretty well in our battery benchmarks so we're expecting big things from this year's larger size.
As for Samsung, it's gone for a 2,550mAh battery in the Galaxy S6. That's a smaller battery than the one sported by the Galaxy S5, and even the one in the HTC One M9, but we'll have to wait and see what software and power efficiency tricks Samsung has got up its sleeve before offering a final judgement.
With that QHD screen to power though, things could get dicey for Samsung if the battery isn't perfect.
Key features
Aside from the looks and specs of the HTC One M9, its Dolby sound improvements, delivering virtual surround sound both with and without headphones is worth mentioning (despite not really being able to hear much improvement through standard YouTube clips.
The all-metal uni-body (available in gold as well as silver) is perhaps the most distinctive feature, though it's a shame the screen hasn't been upgraded to QHD.
The Samsung Galaxy S6, meanwhile, has a fingerprint scanner that's said to be an improvement on the one on board the Galaxy S5 - it can apparently be activated with a tap, iPhone-style, rather than a swipe. Other than that, the screen is the feature we're most excited about.
Verdict
Both the HTC One M9 and the Samsung Galaxy S6 have been out in the wild for sometime now and we've managed to have some hefty experience with both.
We really loved the Galaxy S6 giving it four and a half stars in our full review stating it was, "So close to perfect, but a high price and iffy battery really let it down."
As for the HTC One M9 we didn't like it as much as last year's One M8 giving it four out of five stars. Our verdict read, "A great phone if you're upgrading from two years ago, but doesn't deliver enough changes to be worthy of a perfect score."
Both of these handsets are at the top of their game though with only minor differences between the two and a similar price for each.
I'd recommend reading our full reviews for both handsets before you can work out which is the best for you. Check out our full reviews of the HTC One M9 and the Samsung Galaxy S6.
