I have been fortunate enough to get some extra spools. I went the spool route because it saves space and is less expensive. If you are not worried about either, just get 2 or 3 setups each with different lines. I also think its easier to wallk around with a spool than to walk around with 3-5 rods, But i would recommend you buy the spools as soon as you get the reel! That way you dont have to beg and plead for ones down the road because a lot of companies are always discontinuing or creating new models of the same reels.
In a perfect world I would have a setup for each line I throw. (I would still end up buying spools for each im sure)