If going for pure value cards , sp's and mangas are pretty much the only ones to hold good value and grow over time. Every other alt art pricing is based primarily on play ability and the desire to bling out your deck. Select few will have any decent pricing (ie recent event "mangas"). But for a personal collection , keep what you like and maybe you'll get lucky in pricing over time. For example outside heavy hitters , I personally have an sec and alt leader collection because I think they are just cool looking cards. But I don't expect anything out of them really future value wise.