If you are talking about US/FAA ATP?

If so, it does matter. If you get an ASEL ATP, that does NOT grant ATP privileges in an AMEL (and vice versa).

100% (or 99.99%) of pilot jobs in the US which require an ATP will be AMEL, so I can't think of any reason to get an ASEL ATP unless you have a job lined that requires one, or unless someone else is paying for it. Or you have unlimited money and just want to collect ratings.