Lambda the Ultimate

In my experience they are different enough that spillover is not a danger. That is, if you know in advance that they are not the same language - something no one told me early on...

Probably a good idea, since you'll learn more, and contrast may improve grasp of each, if you are up for a bigger learning experience. It would help to have a good memory and an analytical bent, to distinguish similar things. A feature in one might seem more clear to you after you imagine how to achieve it in the other too. (Languages just make certain things easier; rarely are things denied unless a language forbids them on principle.)

If you work closely with someone, they might find your greater view irritating any time you refer to a language not used in collaboration. Pragmatically, most view this as a waste of time. And a significant minority, perhaps even a majority of devs, have a competitive point of view casting unknown areas of expertise as attacks on their competence, though perhaps only as a social game move (they won't mind you knowing more unless you show it before a witness). You might ask others, since that kind of game is alien to me. Still, aim to get along with people.

There's probably an interesting sub-topic in comparing the two languages, which is the sort of meta discussion that works well as a PL thread.

Thank you both. I am definitely up for the bigger learning experience and plan to essentially write about the experience to analyse the overlap and distinctness of both dialects.

I am learning Lisp on my own so there is no risk there.

I will be sure to return to the forum with my meta discussion as it progresses.

Kind regards,
F

Only tangentially related, but this from Norvig, might be helpful and shows how you can profit from such comparisons.