I would ask this question in the DCC Sound forum... or browse that forum... because it's a very complex subject and not one that you'er likely to get a conclusive answer to, especially via a blog question. For some types the SWD may have the edge; in others Howes will be preferred (and I use that term rather than "better" because as it's sound we're dealing with it's too subjective to be absolute).

In many respects, its possibly more important to focus on what sound you want - as the list of function driven sounds will vary... then there's the installation - speaker chambers and bass-reflex speakers. The best thing to do IMHO is see and hear some sound fitted locos yourself and make up your own mind - which is what I had to do. I've gone for Howes in my Bach 47 (my first venture into this aspect of the hobby)... as I thought the SWD one sounded a bit too type2 Sulzer - but I could be wrong. For others the SWD mught have the edge.. it will for a 55 as Howes don't (won't?) do one. There are independents too. - Go look at the correct forum... and good luck.

Jon