This is a question many home buyers contend with. Perhaps except for the senior citizens, most buyers weigh the pros and cons on a single versus a split level plan. This is generally a question of cost since most split level plans offer more square footage for the money.
This is great if have a big family and need the space, but it also important to consider where the savings is coming from. The most obvious saving is in the foundation and the roof which can be quite substantial. You only need half as much roofing material and maybe 35-40% less material for the foundation.
However if you are considering a home with a crawl space and not a slab, you will have a comparable amount of floor joist. Another place where you potentially save is often a split level plan is a more simplistic plan. Think of a big box sort of plan.
You also should consider some of the added square feet are going to need to be used for the stairs and upper and lower landings. Also sometimes split level plans are the only option because of the prescribed building envelope in the plat. What this means is a one level plan might not be able to meet the square footage requirements for a given community because the footprint allowed.
This leads me to a pro for the split level plan which is a larger yard. Also, two story plans offer more separation if that is something you are looking for say from your kids. Another option you could consider is a single level with a bonus room which is generally over the garage. This cuts down on the noise heard in the home from the second level. But one think you might want to think about is the usable size of that room.