Please note: In the video, I said that backpacks are already moulded on Perry boxes - I meant the little canteens and small sacks and whatsoever, not the big backpacks, which you can glue (or not, if you don't want to). Sorry about that.
This video is meant as a comparison of those two boxes. Conclusion: Warlord Games are more heroic in scale and more bulky, whereas Perry are more realistic. Height is pretty much the same, bulk warries significantly, but they still can be fielded in one army.
Ease of building: Warlord games go together super smoothly, Perry are bit more fiddly.
Parts: In Warlord box, you will have lot of spare parts and can equip your dudes with more SMGs and stuff. In Perry...