What breeds do you have now? And why?
In standard size I paired down to Spitz because they were just as good as Leghorns, but are less cannibalistic and easier to mix ages. As in the Spitz are less cannibalistic than any other chicken breed that i have ever owned. I can often put chicks together that are 4 weeks apart in age.
Also, I have a very rare, highly difficult to replace color.
Then in bantam I paired down to only Wheaten Bantam Ameraucana. I paired down to them because I have some extra good stock, blue egg layers always sell well, the males tend to be respectful, the kids like them. Also, I REALLY like the wheaten color.
Years back in standard I bred pure bred:
Rose comb white Leghorns
Rose comb dark brown Leghorns
(Both excellent kinds of Leghorns that I highly enjoyed, they lost to the Spitz only by a hair)
Black Copper Marans (too few eggs, and eat a bunch. Yes, HIGHLY marketable, but the low production with high feed consumption meant i only had them for a few years before selling them all)
Dominique (didn't lay as well as the Leghorn or Spitz. I love the fact that they are the oldest American breed, and my main rooster had a perfect personality. But, they are not really marketable, and they didn't lay as efficiently as the Leghorns or Spitz)
And then the Spitz, they won the contest of who got to stay.
In bantam
Danvers (I just could NOT get a male that wasn't human aggressive)
The Wheaten Ameraucana
I have had a bunch of other breeds too... I really liked the bantam white leghorns I had, they simply weren't as marketable as the Ameraucana. And I tried several kinds of Wyandotte (both sizes). The bantams are super cute, the kids really enjoyed them. But ..... the standard size don't lay as well as the other breeds, and in bantam the Ameraucana are just as cute, but lay blue eggs which are more marketable. Ages back, when I first got into chickens I bought a few of the various feather footed breeds, HUGE mistake in my climate.
I tried BBS (blue black splash) Ameraucana in standard. For some reason they never excited me.

Their personalities weren't interesting, and they just..... were blah.