There are some strong similarities. The brush dimensions in handle height, diameter, knot width and loft are virtually identical. The shape is very close but there are differences in detail that make it obvious that that the CB2 is not an exact replica. Design is very much a matter of personal taste - I think the CB2 is spoilt by the indented line below the logo. The Trumpers handle is lighter in colour and has the look of a handle made by an automated lathe - but then no claim is made about how the handle is made.
The biggest difference is in the knot - the hair quality, shape and density. No one familiar with Simpsons Best Badger Chubby brushes will think this is a clone. The CB 2 hair is good quality, but has slightly prickly tips and nowhere near the density of the Chubby.
There is too a significant difference in price. The Chubby 2 in Best retails at £120, the CB2 is £100. Probably a fair reflection of relative value?
Finally, performance. I expressed my opinion about the Chubby 2 here. While less dense, the CB2 produces an abundance of lather and the flow through is excellent. The brush is softer and will be more appealing to cream users who prefer to lather in a bowl and paint on the lather. But it will also make an excellent brush for use with soaps and face lathering for those not so keen on stiff backboned short lofted brushes.
Value? Premium prices for premium brand names. If you want this type of brush - these are the sort of prices you have to pay.