It's a funny thing but roughly twenty years ago it was all about large engines. I was building quite a stud of locos applicable to the S&DJR in the 1950s and, as an alternative, the South Western section of the Southern Region up to early sixties ( I had quite a few Bulleids ).
Now, it's all about small engines, dictated not only by my building of small layouts but by the absolute plethora of previously unavailable, but very interesting small locos from the rtr boys..
I do occasionally, VERY occasionally, hanker after a return to running a Bulleid Pacific with eight Mk1s dangling from it or a King Arthur with same number of Maunsells running after it, as I did before but common sense does prevail.
That's why, when you have a large tank engine, such as the Kerr Stuart, it can be a bit of a surprise when it appears. Nothing really comes close to it until we start looking at things like a 94xx Pannier, which again is a bit of a brute.
So, small locos will remain the currency of choice, including small tender types ( bring on the Rapido 01 !) for now at least and not withstanding some rather larger green diesels.
Rob