I've got the choice of two pairs of steering arms for the front of the Coupe. One is quite obviously longer than the other pair.

Which one is best? Am I right in thinking that the shorter arms are stronger and the better choice?

Do they give the car a different feel to the steering, or is there little difference in the two?

Metro ones are longer than Mini ones and are generally to be avoided. They will work with mini steering racks but they do change the angles a bit as you turn. I seem to remember there being a slight difference in bolt hole sizes but I forget the details. I just remember drilling out the mini ones somehow to fit my metro hubs.

I'm not sure if they are metro, or from a Mk1 mini, as they had longer ones too. I'm going to fit the short ones, as they seem to be the logical choice, as everything that I have read seems to point to them being the correct ones.

Tim, mk1 arms are indeed different and are to be avoided, mk2 onwards are what you need. You seem to have made the correct choice
By the way it fits Well sort of

The Mk1 and Mk2 Mini steering arms were not so much different in length but were cranked at different angles. You MUST use matching steering arms and steering rack. There are also Cooper S versions of both these arms. They are significantly thicker in construction.
The longer steering arms are Metro and are not suitable for use with either Mini steering rack.

tim i think i have a set of s arms here, there yours if you want them

I'll take a picture of the arms I have fitted later and see if anyone can tell if they are uprated, or just standard ones.

I've got it all fitted on the subframe now, so I just need to get the rear modified, so that the brakes fit.