
Definitely got my vote on the Rosemary & Co, there not quite up to par with the Windsor and Newton Series 7's, But for the price you could have 2. I find the R&C brushes don't have quite the same spring to the bristles as the W&N's, but other than that I can't feel a great difference in how they respond and hold colour, its not as if theyre all floppy though

they do have 'some' spring.. just less than my series 7's seem to.
Price wise they're approx the same as citadels brushes, but
tbh citadels brushes are pure garbage (except the dry brushes - but Rosemary and Co make mongoose and badger hair brushes that work exceptionally well for drybrushing) while Rosemary and Co are surprisingly good for the price point.
The main difference seems to be in the hair, Citadels seem like a sable blend to me, while R&C offer these, and red sable, I don't think anyone who's used them all will argue that pure kollinsky sable is the daddy, and the others are not even close. The price however makes kollinsky sable hair cost more than gold per the gram hehe!
It only comes from a little weasel type animal in Asia (Siberia)
afaik.
Windsor and Newton also offer sable blend brushes in the name of 'Artists Water Colour sable' These I found worked okay, and lasted me roughly as long as a citadel brush before it simply doesn't know what a point is anymore. Which lead me to think the citadels are a blend. If you consider the price of a blend and then add the citadel tax to it (I'm sure you've noticed they sell things with a huge markup to have their logo or be inside their shop or whatever they deem makes it worth it)
Have a shop around any local art stores or websites that can deliver to you quick and cheaply, The best brushes will be found in the watercolour section and be referred to as Kollinsky sable.
A 'standard' sized citadel brush is approximately a size 0 or a 1 depending on brand... only I think you will find that just about all artist grade brushes will come to a point better than a fine detail citadel does at any size of brush (even a 16)
lol!