There is no best, only
what works best for you.
Check with Micro Mark,
Caboose Hobbies as a start. There are other good online comanies. You did not say Diesel or steam? N scale
or HO scale? You will get many hits. Come back here and ask about the
company selling the locos.
Do a Google search for
diesel tsunami or steam tsunami. Get on the Athearn email list.
Athearn/Roundhouse are going to the Tsunami decoders. Go to the
Athearn site and look around.
I got an email from
Athearn some months ago about the Tsunami decoders being put in their
locos.
Bachmann right now has the
Tsunami decoders in their steamers.
Be advised, the products
come form China and come in batch shipments and can be sold out in
about a year.
Right now some are waiting
shipments so the products may not be available yet.
Best bet is to do some
homework and search the Internet.
I have no idea about other
manufactures of other locos.
Rich