Unless you need the portability of the 4 section, the 3 section would be ideal because it is more stable when extended. They are both just as sturdy if you don't extend the legs though, which is often how I'll shoot landscape. If you can mess with it before you buy it that would be ideal, and if not, be sure to check it out as soon as it arrives. REALLY test the stability. If you're on a tight budget, you can give up most of the features of fancier tripods, but not stability, that's the reason you have it. Make sure the thing is a rock, and if it's not, send it back because you'll end up replacing it anyway. It's not a brand thing either, quality varies a lot from model to model. When I was tripod shopping I had ordered a Gitzo Explorer. Gitzo has a great and longstanding reputation for tripod quality, and the explorer was priced right alongside all of their top of the line models, but it was not stable. Lots of cool features, and every possible position you could imagine, but that doesn't mean anything. I can hold the camera at a weird angle unsteadily with my hands, I don't need a tripod for that. I ended up exchanging it for a Mountaineer after 2 days, and it is extremely stable, though more limited in features.
Just make sure you end up with something that will never make you want something more solid.