You'll get hundreds of recommendations but everyone has their own preferences, loft, knot shape, natural v synthetic, backbone, splay, handle shape, colour etc.
Firstly you need to decide why you want to replace it. There's no need unless it's shed so much it doesn't work, but lots of us just like trying different brushes to see where our preference lies.
Somewhat oddly, amongst the 5 or 6 that I have, I find myself reaching for the Yaqi Moka Express synth, even though I've got a Simpson best badger and other boars, badgers and synthetics. I was surprised by this as I really only bought it for the shape and colour of the handle, being a coffee nutter. But it just feels right and lathers nicely. My heart says why big up a mass produced Chinese bit of plastic when you have classic British, or nice wooden handles. But it just suits me. It's nice to change it up a bit too, some days are boar days, sometimes I like the big floppy PAA phantom aero, but 4 days out of 7 I grab the Moka. I think if you are in the mood for a new brush, there are many to try at low price points.
