They are both of the same mold - the saddle soap base. Neither have any middle/heart notes which make them rather interesting frags. No spice, no florals (although they may use geranium), no herbs. Both have citric top notes the saddle soap base, and well, that's about it.
Where I think English Leather gets it right is in the sparkle in the citric notes which manage to linger through the drydown, and the saddle soap is a little bit dirtier compared to REL. I find it almost magical.
The mandarin in Royal English Leather is muted, relative to the zest in the English Leather.
However, that doesn't mean I don't like REL. In fact, I prefer wearing REL. For as much as I like English Leather, it can be a tempermental beast to wear. Just a little too much on and yerch! It can be overpowering. Both have comparable duration on me, but I might give the edge to REL. On some people it lasts forever. REL is mild mannered on me and I could probably wear this one any time any place ... whether anyone else but me can smell it, well that's a different matter. I think the English Leather would win the siliage battle.
Anyhow I have a similar reaction to Brut vs. Rive Gauche PH. They are similar in a number of respects, but I adore the Brut. Still, Brut is tempermental and Rive Gauche is much more mild mannered (along with better duration).
I have a severe problem with the stick English Leather deodorant. The fragrance in that is way too strong. (I have the round alcohol based deo, I understand there is a non-alcohol based one... I think it might also not have any aluminium for health nuts out there.) Fortunately I shaved my pits (I'm sure everyone really wanted to know that) and now I only need to apply a little deodorant so the EL stick problem is amerliorated somewhat. I like to use the EL deodorant (extremely lightly) with REL as well.
I was not impressed at all with English Leather Lime. I have English Leather Musk but I don't recall my position on that.
Please note that in the past I used to compare Knize Ten to REL, however that was primarily because of the mandarin top notes with they share in common. All I used to get were the mandarin notes in REL when I tested it at Saks and from when a fellow BNer generously sent itSince getting my tester of REL, I've been able to actually wear the frag and I think it might be better to compare REL with English Leather and to a lesser extent, Equipage which also tries to emulate bridal leather.
Knize Ten is a more modern frag with a developed top - middle - base which I have always thought of as a tobacco frag (from when I tested it in a mystery scent challenge) than a leather frag, but it might just be me! I haven't worn that in a little bit. It might be time for me to actually have a mandarin battle to see how REL, Knize 10, Royall Mandarin & Pierre Cardin Centaur Cuir Fougere stack up (maybe I'll throw Happy for Men in to see how it stacks up too.)