I had this decision to make earlier this year...except I didn't want to spend this much money.
Everyone told me not to do a deck because of staining every year, nails popping up, splinters, and eventually rotting.
For my size, 24x12, a poured slab was going to be more than I wanted to spend, so I did the next best thing.
Lowes and Sutherlands has 24"x24" patio pavers in a few different designs. They are $10/each and weigh about 100lbs. They are large enough to span over slight ups/downs in your yard and heavy enough that they don't move.
We didn't have anything so we killed the grass, leveled the dirt w/ some topsoil decently and just laid them down all lined up. Took us a Saturday to do, and cost me like $6-700.
It looks great, is very nice to walk on, and overall I'm very happy. We ended up having to fix like 4-5 pavers that would 'wobble' if you stepped on them, but all we did was tilt it up and throw some topsoil under the lowspot and set it back down.
Very easy and cheap, not sure what the long term will be, but we'll only be here another couple years, so I didn't want to spend a ton.