Looking to replace the rear drop links next year (along with other rear suspension work). Car is Focus Estate 2008 1.8 TDCI 

Under the car the drop links are the first photo, just solid rubber.

The other rear drop links that show up as fitting are more of a ball joint design (other photo).

Are these interchangeable, is one type better than the other (why), or does only one type fit and not the other (i.e. eBay parts not precise enough)?

They aren't interchangeable.  One has straight mounting points.  The other has 90 degree mounting points.

I thought estates used straight ones and hatches used right-angled ones but that theory was challenged on here previously.

Thanks Tom, and good morning.

My estate has the straight ones, so I thought as you did.

But as you said the 90 degree may also fit, so I will look into it, even if as expect the default ones are the straight.

14 minutes ago, TDCI man said:

But as you said the 90 degree may also fit, so I will look into it, even if as expect the default ones are the straight.

They aren't interchangeable.  The ARB ends are angled differently on the car.

A picture tells a thousand words. Very helpful Tom. Will be tackling the rear suspension in the spring.

Heavy rust on the rear ARB ends. Put on some ACF50 to protect until spring. Hope to restore the worst in situ if I can. Good to be aware of the ARB ends as you pictured in case another needed.

BTW after the load of work I've done, on some of which you've been very helpful, car started first time. Done a few miles to be laser aligned. Nothing untoward so far. Will update (also solid flywheel in, which may interest members) once the car has done a few hundred miles.

My pre-facelift 1.6 petrol LX hatchback has straight rear drop links.

It was built at the Valencia (Spain) plant in late 2005.

Perhaps the type of links used changed over time or with different build locations.

Well, mine is a 2008 estate built in Germany and I have looked and the drop links are the straight ones as Tom has posted