HTC launched the One M9 as its new flagship handset. Luxury design, new components, a revised Sense experience all fused together as the handset to set 2015 alight. 

But HTC's plans globally don't reflect those we see in the UK or the US, with a number of other handsets appearing in Asia, presenting a number of alternatives that many of us will never be able to buy. 

We've reviewed the HTC One M9, but here's the rundown of how HTC's other top devices compare.

HTC say that the One M9 is the flagship, the lead device. But then there's the One M9+, which offers much the same - a premium full metal body design, with exquisite attention to detail - but steps up in size and functions. 

The E9 and the E9+ are down a level. These are the "plastic ones", but their size means they're really pushing into phablet territory. Of these two, the E9+ is the higher spec device. 

Then there's the One ME. As the name suggests, this is sort of a fusion of the M and E class of devices. It adopts much of the skill of the One M9+ on the front, but with the E9+ rear, more or less.

All these devices run Android and HTC Sense, although there's different services available in different territories. Only the M9 is available globally, the other handsets are available across Asia in various countries.

The HTC One M9 has a 1920 x 1080 pixel resolution, at 5-inches. That gives you 440ppi. That's the same as the M8 was last year, a good size with a good resolution.

But it's not a display that anyone is going to be getting excited about, not when others (Samsung, LG) are pushing size and pixels. It's the smallest of our selection, as both the HTC One M9+ and the One ME have a 5.2-inch display and both offer 2560 x 1440 pixels, for 564ppi, which is much more "next-gen" on paper at least.

Yes, that's incredibly sharp, offering a Quad HD display. But the One E9+ also offers 2560 x 1440 pixels, this time at 5.5-inches, the same as the LG G4, with 534ppi. 

The One E9, settles for 1920 x 1080 at 5.5-inches, which will be the softest of the lot. Of all these devices, it's likely to be the M9+ and ME that are seen as the most progressive, although resolution and size isn't all that matters in a smartphone display. 

If there's one thing that's noticeably different in 2015, it's how manufacturers are selecting the hardware to power devices. It's not all top-level Qualcomm any more - the LG G4 takes a Snapdragon 808, Samsung used its own Exynos. 

Except the HTC One M9, which takes the Qualcomm Snapdragon 810 chipset and pairs it with 3GB of RAM to good effect and rather predictably. HTC has a long history with Qualcomm.

HTC's other devices here use MediaTek, all are 64-bit octo-core CPUs, and they all get 3GB of RAM, apart from the E9, which settles for 2GB. All should be speedy in operation, given that there's plenty of power. 

In terms of storage, it seems that 32GB is also the standard, except the E9, which starts at 16GB, although these things differ by region. All also accept microSD card for expansion, which is a handy option.

Moving to another chipset is likely to be about price and branding. Qualcomm is well known in the US and UK, but MediaTek less so, unless you're a smartphone fan. That's likely to change however, especially with a move along from Qualcomm dominating the chips in all leading devices.

If there was one area that the M9 really stumbled in our review, it was in the camera. The move from UltraPixel and Duo Camera on the rear for a straight-shooting 20-megapixel sensor, doesn't seem to have quite worked out. 

But across these handsets, there's a blistering array of difference. Firstly, let's start with the front camera: all offer the UltraPixel on the front as a selfie camera, which we think is a smart move as it gives great results. 

There are some territorial differences, however. The E9+ in India, for example, has UltraPixel on the front, but in China it offers a 13-megapixel front camera, which is really playing the spec sheet game: higher numbers look better on paper, even if they don't perform better.

As for the rear cameras, the M9 has a single 20-megapixel sensor, as does the One ME and the One E9+. We'd expect the performance to be similar across all devices.

The One M9+ keeps Duo Camera, however, offering a 20-megapixel main sensor with the second sensor for depth information. Duo Camera wasn't so well received on the M8, which we suspect is behind the change, but it's interesting that HTC is still invested in the technology.

The One E9, on the other hand, settles for a 13-megapixel sensor and it's the one handset that doesn't give you 4K video recording, despite having the power and pixels to do so.

One of the hot features of 2015 seems to be the fingerprint scanner, especially with talk of Android Pay coming later in the year. 

The One M9 doesn't have a fingerprint scanner. Of all the devices we're looking at here, it's limited to the One M9+ and the One ME. All the others miss out.

We've given you a quick rundown of all these smartphones that bridge a segment at the top of HTC's portfolio of devices. 

The HTC One M9 was first launched as the flagship and for many of us and it's the only device we'll see. The M9+ is the M9 on steroids and will probably be seen as the most progressive or competitive device when paired up against the likes of the Samsung Galaxy S6 or LG G4.

But the One ME is also impressive. It's impressive on the spec sheet, as is the One E9+, accepting that they are a step away in terms of build materials, but potentially offer much the same experience in a more affordable package. The One E9 is a noticeably lower spec device. 

Why does any of this matter? Because HTC said that there will be another hero handset launched in October 2015. We suspect it will offer a 5.2-inch display, we suspect it will be 2560 x 1440 and we suspect it will have a fingerprint scanner, based on what we see elsewhere in HTC's portfolio.

Until then, however, you'll have to look at all these lovely devices and dream about those you can't actually buy.

READ: Best smartphones 2015: The best phones available to buy today