Which one should I buy

Arduino Pro Mini which is a favourite of mine.

This: http://www.ebay.co.uk/itm/Pro-Mini-Atmega328-5V-16Mhz-Rep-ATmega128-nano-Arduino-Compatible-UK-STOCK-Fast-/181738194992?pt=LH_DefaultDomain_3&hash=item2a5070c830

or this:

http://www.ebay.co.uk/itm/Pro-Mini-Atmega328-5V-16Mhz-Rep-ATmega128-nano-Arduino-Compatible-UK-STOCK-Fast-/181663231403?pt=LH_DefaultDomain_3&hash=item2a4bf8edab

The latter one appears to have a very beefy linear regulator - maybe it can achieve better outout pin drive capability?

Any comments ideas?

YET ANOTHER STUPID PINOUT FOR THE PRO MINI! GODDAMNIT! NOW THERE ARE THREE! And this isn't the best of them, it's got off-grid pins for A4-7, but not in the same place as on the official (less perverse, all else being equal, but just offsetting them 0.05" would be so much better, but no they had to center them), and still no ISP header...

The one with the better regulator is the one I'd pick if I was planning on powering it off an external supply, particularly if I was pushing the regulator - but bear in mind that this will not effect the chip's output drive strength, as that is limited by the chip, not the regulator - that only improves output on the regulated supply pin, so you can switch larger loads with an external transistor/etc, while still powering them off the Arduino. You still can't do anythign that requires serious power though - it's still only rated at 800mA.

If I wasn't planning on doing that, I would get one with the good pinout:

http://www.ebay.co.uk/itm/New-Pro-Mini-atmega328-Board-5V-16M-Arduino-Compatible-Nano-Hot-Sale-IDXX-/271726971992?pt=LH_DefaultDomain_3&hash=item3f44308c58

Or at least the one with the official pinout:

http://www.ebay.co.uk/itm/PRO-MINI-ATMEGA328-5V-16M-MWC-avr328P-Development-Board-for-Arduino-/281675890095?pt=LH_DefaultDomain_3&hash=item419530fdaf

Over the past two years I have bought a dozen or more pro minis from ebay and from various suppliers, and never looked at the pinout!

I was aware that the ebay ones had the A4-A7 lines conveniently at one end and that the genuine had them in peculiar places.

But I was not aware all this time that there are variations to the theme!

Not until I read your post above.

Suffice to say, somehow, all my pro minis, have the same pinout, the one you do not like. Coincidence.

I bought the larger regulator one.

By the way they all have a Serial header at one end and the A5-A7 lines at the other end, but no ISP header as you said. I typically flash my own bootloader before soldering the mini on the PCB,

I've been buying the AMS1117 regulator ones for over 6 months now, I like having the beefy 3.3v regulator on the 8MHz one. I wouldn't count on pulling more than 300mA though, there simply isn't enough cooling capability to go up to the 800mA that the regulator can theoretically handle. It can power an ESP8266 module though which was my target.

I believe this is the actual original maker's aliexpress store: http://www.aliexpress.com/store/721718

Minor hint, but makes things just a little easier:

When citing eBay links, remove the question mark and all following - it only identifies the eBay session you were using when you looked at it.