Foamboard vs cardboard for dioramas - which is easier?

Foamboard is definitely way easier, honestly 😅 It cuts clean with a utility knife, it doesn't tear up like cardboard does, and it holds weight better if you're gluing stuff on top. Cardboard gets wavy if you get it even a little wet (even by accident) and ends up looking all wrinkled, while foam stays flat. If it's your first diorama, I'd go with foam without question.

Cardboard is going to frustrate you if you need straight, clean edges, because it tends to fray even if you use a ruler. Foamboard is more forgiving in that respect.

That said, it really depends on what you want to do. If your diorama is small and is only going to have light decorations (little paper cutouts, plastic plants, that kind of stuff), thick cardboard works perfectly fine and it's cheaper. It looks just as good painted. The problem comes when you start hanging weight on it: large figures, structures, glued-on accessories. That's where foamboard keeps its rigidity without warping or sagging.

Another advantage of foamboard is that you can carve it to make more complex shapes without it breaking on you, and contact cement or hot glue stick to it beautifully. With cardboard you have to be more careful because it can get saturated with glue. If it's your first diorama and you want something easy, foamboard saves you the stress. But if you're just looking for a basic support for a simple scene, cardboard does the job without complications.

If what you need is something quick and hassle-free, foamboard wins hands down, but there's a detail that changed my life: cardboard becomes way more manageable if you let it rest for a couple of hours after cutting it, because it releases the internal tension and doesn't warp as much afterward. Either way, if your diorama is going to have heavy or wet elements, just go with foamboard - cardboard simply isn't designed for that and you'll end up with a disaster on your hands.

I made a forest diorama not too long ago and honestly, I switched to foamboard after getting frustrated with cardboard on previous projects. The difference is in the details: with foamboard you cut with a craft knife and the line comes out perfect the first time, whereas with cardboard you have to make several passes and even then the edge crumbles. Plus, if you need to glue trees, figures, or whatever, foamboard holds up way better without warping. With cardboard, after a while and with the humidity in the air everything gets wavy.

That said, cardboard has its place. If your diorama is small, without much weight on it, and you only need smooth background walls, it works fine and it's cheaper. But if you want something that'll last, that looks neat, and where you're going to have things glued or hung, foamboard saves you a ton of time and headaches. It's worth spending those extra pesos.

Don't go for foamboard just because it's "easier" if your diorama needs delicate details or textures - that material looks really flat and artificial if you don't finish it properly. What nobody mentions is that foamboard soaks up glue like a sponge, so if you use white glue or something similar it'll end up sticky and warped at the joints. Cardstock has its downsides with the edges, sure, but if you work it carefully (sharp craft knife, multiple light passes instead of one heavy one) it gives you way more versatility for textures, natural folds, and realistic finishes.