Mirliton, usefull from around 1515 onwards I dare say, when the Landsknechts/Swiss fashion was adapted in parts by Italians, French and Spaniards.
The Perrys as delivered in the box will not work for the Italian wars, with the exception of the 1494/5 campaign (though the Swiss wore their hair long in that campaign, according to contemporary illustrations). Some may work for later Italians and Swiss if using other heads, but not for long.
They DO mix well, however, with the Warlord Games (Pro Gloria) plastic sets and the Steel Fist heads, so you can create many interesting characters and units. The close fitting clothes are good for the Italian style, and the Barbuta like helmets give the floppy bodies a nice Italian touch. That said, it only works so far…
If historical authenticity is not strongly enforced, mixed units make a far better standin for this era then pure Perry infantry, especially for units that are not covered by any company like French or Spaniards of the 1510-20 era.
BTW: Somewhere on this site is a posting of mine with various conversions of both kits.
The main problem you face is the kind of army you want to build. The fashion in the Spanish, Italian, French and various Imperial forces varied, and SOME units changed their character each decade (others did not, or slower).
I do own the Artizan Landsknechts and think they do not go well with the Perrys, both from size&bulk and from style. I use mine for Swiss elite from Marignano to Naples.
If you want to use them, the Perrys are best suited for Italian units until around 1515, which showed up in almost all armies. The Mirlitons show you what Italians think the Italians of the 1520ies looked like, and if you look at contemporary paintings of Ravenna to Pavia you wont see anything resembling these.
If you want to use them, build an army of around 1500, perhaps Cesare Borgias Romagnols, or the Venetians for the 1509 war. I am currently assembling some 60 cavalry and 200 infantry of the Perry sets for the Burgundian and Reichsheer conflict, around 1475 – though of course most will work for the Swiss wars and the later conflict between the Burgundian army under Maximilian and the French up to 1493.
What did not change, or only slightly, is the heavy armour. If you put a Landsknechts head – preferably one of the splendid Steel Fist heads – upon a Knight of the Perrys, be he mounted or afoot – it looks perfectly like a minor unfashionable leader of an Imperial or Landsknechts contingent of 1500-1532.
Sorry for the rant :-)