I have a large WSS collection from several manufacturers:
Dixon - undoubtedly the best in terms of anatomy, detail, size and "character"; unfortunately, the range was never finished and there are considerable gaps.
Roundway - most comprehensive range for both WSS and GNW; slightly larger than Dixon, but not noticeable when painted.
Minifigs - standard effort by them: lots of different types (though less comprehensive and accurate than Roundway) in the characteristic Minifigs poses! Very few specifically GNW figures; larger than Dixon.
Irregular - lots of figures (second only to Roundway in terms of overall coverage - probably better for GNW); not great in terms of detailing (I don't have any Editions Brokaw figures, but from what I've heard of them I'd say Irregular are on a similar level in this respect). Smaller than Dixon.
Lancashire - very disappointing; infantry ok-ish (but very large - easily the biggest "15s" in this period), but their one-piece cavalry are awful, IMO - think 15mm horse, with 20mm rider wearing 25mm hat! Shame, because their AWI and Scots Jacobites are quite good - looks like they used a different sculptor for their WSS and 1690s range.
Essex - usual problems with infantry doing the splits and the horses with short legs; however, some of the infantry poses ("at attention" and "at ease"), the gunners, and the rearing/plunging horses provided in the generals packs are superb. No specific GNW figures, but the infantry at ease in the high "English Guards" mitre and tricorne are perfect for Saxons. Slightly bigger than Dixon, but hard to see when painted.
Hallmark - mainly 1690s range (League of Augsburg), but with a few tricorne figures added and many figures in the "older" uniforms can still be used anyway. Noticeably smaller than Dixon, which is a shame as theirs are the best horses of the lot (I put their riders on Dixon horses). Magnificent range of carts and wagons - Museum Miniatures are also good for these - and "extras" such as highwaymen, monks, roadside monuments etc.
Hope that helps.