Birch plywood or 2x10 for weight saving?

[gringogigante]

I need to build some truck bed tool drawers for my ranch truck.  What weighs more in your opinion....1sf of 3/4" birch plywood or 1sf of 2x10?

[Carver]

Comparative weights isn't a matter of opinion but of physical fact. And why is weight a factor?
Let's start with how you plan to construct these drawers; is the 2x, which is actually 1-3/8", to be used in the same application as the 3/4"? As drawer sides?

[gringogigante]

Comparative weights isn't a matter of opinion but of physical fact. And why is weight a factor?
Let's start with how you plan to construct these drawers; is the 2x, which is actually 1-3/8", to be used in the same application as the 3/4"? As drawer sides?

Yessir.  So I planned on using 1/2" birch ply for the bottom and 3/4" birch ply on top (for more load bearing strength). For the drawers I'll use 1/2" birch ply for the bottow.  But for the sides of the box and drawers, I'd like to make it strong AND save some weight if possible. So I'm looking to see if a 2x10 pine board or similar sized piece of birch ply would weigh more.

[Carver]

Construction lumber is not kiln-dried enough to eliminate all shrinkage and twisting, so if the drawers are going into a cabinet allow for that. The more weight of course will require higher load bearing drawer slides, which can dramatically increase the cost. The post title calls for "weight saving" but now you mention you want weight, so please clarify.
1/2" birch, or marine, ply is strong, but can get very expensive and might be overkill for a bottom. You'd be surprised, if you don't know it already, that there is a 1/4" ply that is used for floor underlayment that is light and extremely resilient. A very strong drawer for tools can be built using that for the bottom and 1/2" ply for the sides. But I would dado the drawer sides & front/back 1/2" from the bottom, 1/4" deep and glue and nail (staple nail) 1/2" x 2" wide ply slats horizontally to the sides under the bottom at the ends and middle. If you use drawer slides, with the drawer construction mentioned, or any for that matter, take note of where the screw holes for the slides will need to be on the drawer sides as you do not want them to be at the same location as the dado on the other side.

[FreeLancer]

https://www.engineeringtoolbox.com/wood-density-d_40.html

From this table, it appears that in the exact same dimensions, a pine board will be lighter than a similarly sized piece of birch.  However it's not half as dense as birch so I bet the 3/4 baltic birch will be heavier than the pine 2x.  Whether it's as strong?  I don't know, but as long as your joinery method isn't sabotaged by the relatively weak edge grain, I bet the plywood is good enough. 

For your proposed usage, on the sides of the case and drawer, it seems to me like a 2x10 would be plenty strong and might simplify the joinery at the expense of a couple inches of drawer width.  I could see pros and cons to both, though.

[FreeLancer]

A little more digging around on this Finnish site turned up a density of 680 kg/m³ for Baltic Birch (a specific term for a high quality plywood product, not a species of birch), which seems to be just slightly more than unlaminated birch from the table.  I guess it makes sense that the glue and compression involved with making the product would increase the density.  So, depending on the exact sample of pine, it's possible to get a density as low as 350 kg/m³, which is very close to half the density so 2x pine and 3/4 Baltic Birch could (theoretically) be close to equivalent weight.