Depends somewhat on which Crusade you want to do.
My blog is generally the 13th century so only covers the later crusades but some of the comparisons may come in handy.
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Legio Heroica have good figures for the 3rd and later Crusades. I don't think they mix too well with the other ranges which may be a reason to go elsewhere.
If you want to mix, then on the whole Donnington, Mirliton, Outpost and Old Glory knights mix well (as long as they do figures for the Crusade you want). The foot from these plus the Black Hat infantry also mix.
Ranges I haven't compared on my blog –
Mirliton have a newish range which would suit the 2nd Crusade and some of their other figures would also suit the 5th/6th Crusades.
Donnington now do figures for all of the Crusades with some of the Normans suitable for the 1st Crusade.
Touller do some good figures but the website seems to have been down for a while now.
Essex are popular but I don't think their figures for this period are some of their best.