Both brushes have a knot width at the base of 23mm. Both are 92mm high. But the brushes are completely different. Partly because one is the very soft silvertip while the other is best badger. Simpson's best badger brushes are however surprisingly soft also. The difference lies in the height of the loft - the height of the brush head. The difference is just 4mm. If you have a 'floppy' brush, tie a piece of string round the base of the knot around 4-5mm thick to simulate a lower loft height and feel the difference. Suddenly, the silvertip will be much firmer. This may not suit you. But if you prefer a brush with some backbone which is preferable for face lathering look for a brush with a relatively low loft. Larger knot sizes can afford higher lofts. A firm brush in the 22mm knot size needs to be below 50mm. Rooney do an excellent silvertip 22mm/45mm loft which is an excellent face latherer. If you prefer the luxurious feel of a soft silvertip, mix your lather in a bowl with creams and paint it on, the loft for a medium size brush can comfortably exceed 50mm and you will be happy. If you prefer soaps and face lathering with circular motions go for a firm brush with a low loft. Always check dimensions before buying a brush. They are usually set out clearly on most web sites.
To explore further the opinions of shaving enthusiasts take a look at these threads about knot/loft preferences: