I guess you have too less time to do a lot. You will arrive at Terminal 1/2/3 which is completely ugly. Indeed, if you are into exploring airports, then after your arrival just stay airside, stroll round a litte, watch a few Spanair, Air Europa and Ryanair planes... But again, this place is NOT nice. You would probably like to leave for Terminal 4 quite soon with the bus. You can do this landside if you wish, too.
Terminal 4 is much nicer. Keep in mind that the LAN flight is considered as a Non-Schengen flight, which means you will depart from the satellite, you will need to take the little subway and also pass passport control. This takes a little more time. And since T4
is great and you will be at the satellite, better spend the time there and watch a few longhaul planes, they have nice shops in T4
, too, and in my opinion better food options than at T1/2/3.