Gentlemen;
Just my humble opinion, but answering this question with any reference to Testudo is a bit like telling someone looking for a new car to find a DeLorean or a "new" Jaguar XKE. They may be wonderful, but if nobody is producing or selling them (legitimate castings), what's the point? And Matchlock isn't much better until they work out their production problems.
So, soapbox aside, if you're looking for complete ranges still in full production (and likely to be barring something unforeseen), then the answers are:
Peter Pig – Complete, some excellent sculpts, but small figures, don't mix well in the same units with other makers, these are "true 15's".
Gallia (available through Warrior) – An older, smaller range, not really very complete and they don't mix well with most of the other figures mentioned.
Freikorps15 – Complete, some excellent sculpts, larger than PP but smaller than some others, closer to about 16 or 17mm, won't always mix in the same unit, but do look good in separate units in a mixed army.
Essex – Complete, some complimentary figures available from other ranges, mix well with Freikorps15 and some others, they have their own style and people either love them or hate them, I like them very much in selected roles and love their horses (which they will sell separately).
Donnington – Way beyond complete, one of the most comprehensive ECW and TYW (and even Dutch Wars) ranges around, slightly chunky but clean sculpts and castings, mix well with Museum, Irregular and Black Hat and some Essex and Freikorps15, also available individually letting you mix a few in here and there.
Black Hat – Slightly larger figures, will almost mix with Testudo, but will mix with Donnington's, Museum, Irregular and Old Glory, fairly complete range
Museum – Reasonably complete range (I would like to see a few more figures added), good sculpts, mix well with Old Glory, Donnington, Irregular and some Essex and Freikorps15.
Lancashire Games – Not mentioned yet, larger figures, very inexpensive, very animated with reasonable sculpts, paint up well, will mix with Testudo and some of the larger Donnington's in size, fairly complete range
Old Glory 15's – Very complete range, and offers a companion TYW range with figures that will mix, great variety of poses in each pack, very animated armies possible, all the sculpts are not as sharp as they could be (particularly faces), but they do reward a good paint job. You could do an entire collection with just OG and still have a lot of variety and animation, but they also mix well with Museum, Essex, Donnington, Irregular and Freikorps15.
Irregular Miniatures – Very complete range with some complimentary types, not my favorite sculpts by Ian Kay, but presentable and paint up well, mix well with OG, Museum, Donnington, Minifigs, Freikorps15 and some Essex, also available as individual figures letting you mix a few in here and there.
Minifigs – Complete range with complimentary TYW figures available, mix well with Donnington, Museum, Irregular, Freikorps15 and Essex for size. Some poses a bit "stiff" but still very good figures. People either love or hate Minifigs horses, but their riders will fit on Essex horses and some others.
I think that's all, but I probably missed someone who will get their knickers in a bunch. BTW, here's the comparison photo I did of ECW Scots. Shown here are (l to r) 2 Museum, 2 Freikorps15, 2 Old Glory and 2 Essex. The grid is 4mm X 4mm with incremental marks at 2mm so that you can judge the overall size.
picture
Bill