It all depends on what you want...If you want to get poly bushings, you cannot get the control arms with those already in. You will end up spending about the same amount either way that you go, so it is totally up to your preference. I'm in the process of replacing ALL of my front suspension parts as I type this. I re-used the lower control arms, and had a new ball joint pressed in. New shock shock mounts (referred to as strut mounts) are not currently available in poly so the plain rubber moog part is our only option right now. The upper control arms you will have to purchase. The upper ball joint is built into the arm instead of pressed in. The upper poly bushings are pretty easy to get in after you get the stock rubber ones out.
If you plan on just replacing the worn bushings with OEM rubber ones, then get the complete lower control arms. Uppers as I stated you will have to get regardless if the upper ball joints are shot. While you're in there, I'd recommend replacing the outer tie rod ends as well. I'm doing significantly more than that, but that would be the minimum that I would recommend just to replace most of the parts that wear over time. I'm also replacing the spindles (upgrading to '93 and up), hub bearing ***'y, rack and pinion, and I think that's it! I'm sure that there's more, but that's all I can think of right now.
Bottom line is if you're going poly, use your old parts, (lower arms). If not then just buy the replacement lower arms.