I don't have a lot of experience with these external drives but if you want to be assured of no problems then go with the Apple version. If money is more of an issue, I would fully expect even the lowest priced units to work just fine. It's your decision if you want to spend a little more for guaranteed success or spend less and possibly have to exchange the one you bought for a more expensive model.
Once you install OSX, you no longer need the drive. In fact, you can create a disk image from the OSX CD or DVD and use that disk image to make a bootable USB stick later on. I have installed OSX from USB sticks countless times (on Intel Macs). On my old G4 Mac mini however, I'm at the mercy of rotating media (but I haven't switched the thing on in over a year.

).
Here is one I found on amazon.co.uk for £27 that says it is for Macs. So for less than the Apple drive you have one that the sellers says works. The only drawback is it has no reviews.
Here is another one for the same price that has 2 reviews, both by Mac users that said it worked for them. Both advertise free delivery in the UK.