Yeah, I am WAY late with this, but I've missed the other two bat-arounds and decided I needed to get back into the fray (not the group, though they are quite good).
The question posed is this: which set will increase in value (or at least maintain it) in ten years?
My answer is simple: Oddball cards.
My explanation: The first cards out there were rooted in tobacco, then bubble gum, cereal, sodas, you name it. Oddball cards will be harder and harder to generate because of the crazy licensing issues the MLB has, and the MLBPA as well.
In the past, when a company wanted to make baseball items, if they didn't licensing rights to logos and such, they just airbrushed the logos off. the player's name, position and team would still be seen on the card.
Today, if you were to do something similar, you could face lawsuits based on the fact that you used the name of the player without express written permission and used the team name without express written permission. heck, I'm not even sure you'd be safe using the player's image at all without permission of the MLBPA these days.
So, how does that affect the future value of such cards? Oddballs have generally held pretty good value based on their novelty and inherent rarity. they are not produced in as many quantities as big company cards, so they are harder to come by. Some are regional and can only be gained through the mail, trading, online buying.
Though not necessarily 'baseball,' the Bill Clinton 3-card set produced by/for the Hot Springs, AR, Chamber of commerce/visitor's bureau, is a good example. You had to be at certain events to get them, or know the right people (I fall into the latter category, having done computer/network work for my area US Congressman). Of course, now you can find these cards on eBay and I think you can still buy them i certain places in Arkansas. Aside from that, though, they are a hard find.
As time marches forward, oddball items like Pepsi Lid Liners, Milk Bone All-stars, tattoos, and even Post cereal cards will be harder and harder to find. This inherently drives the value upward because more and more people will pay more and more for those items.
I also think that as the players who are/were featured on such items age and pass on from this life, those items will continue to gain value. I don't know why it is that something should become more valuable once the person on that item is dead, but that is how the world of collectibles seems to work. the same will hold true for the oddball item.
I personally love oddball cards (or what can be loosely referred to as cards). The photography is usually the equivalent of having taken the photo myself (or worse), and they usually come in various shapes and sizes. I would venture to say that making such diecut items is fairly expensive these days, which might also explain the decline in custom-shaped cards. Though mainstream, Pacific was great at the diecut oddball card. I wold love to see another company make tree ornaments, 3d boxes, etc, the way pacific did...
I hope the days of the oddball cards are not behind us, but I am afraid they are just that. In the wake of their disappearance will be their value among those who appreciate the art, humor, and creativity of their makers.