You are probably expecting another treatise on the value of PDFs over paper books. I feel that path has been tread over sufficiently. This is about the FUTURE! Oooooooowwwwweeeeeeeeooooooo
In the video game industry, there is a big push toward microtransactions. In a worst case scenario (like Star Wars the Old Republic) you are charged for nearly every feature of the game, even those that are purely cosmetic. Content is being held hostage in an effort to squeeze more dimes from the player.
Then there is iTunes, you don't own that music you have purchased. You have leased it. If you were to switch to a "not iPhone" and quit using iTunes, all of the music you had thought you had purchased would no longer be available to you. This motivates you toward staying with their product. The longer you use their product, the more painful it will be to switch.
Dungeons and Dragons used to follow a similar paradigm, getting players to invest a large amount of money into various books. In a sense, Pathfinder is worse as it not only continues that philosophy but as a Game Master of the Pathfinder Society I have too keep my library update because the scenarios for each new season require rules from the most recent books. What remains to be seen is if Paizo (the makers of Pathfinder) are going to engage in the same disaster as WotC once perpetrated: the new Edition.
Imagine you had spent over $400 in rule books for the game of your choice and then they came out with a new edition 6 years later that made all of your purchases obsolete. What incentive would you have to buy into the new edition? The D&D fanbase may be the largest in the RPG community but it is also the most fragmented. Their are groups who have refused to update beyond the edition they originally bought into. Many of the 3rd Edition fans went to Pathfinder. As a result Wotc has lost some share of their market with each new edition.
Now let's look at World of Warcraft. Recently there was an unauthorized vanilla server that ran the original WoW before any of the updates, patches, or expansions. By some reports it had over 800,000 active players before it was shut down by Blizzard's legal department. But it brought to light that the game had evolved into something very different from the original and that unless you engage in illegal activity, you can never play that game experience again.
But therein lies the beauty of owning pen and paper RPGs. We can ignore the update or the new edition if we want to. We can lock ourselves into the game version we love as long as we keep the books. A system with a good core book is all you need. The micro-transactions of maps and figurines are not necessary. And with a hobby like ours, forcing us to lease the product rather than own it is difficult (not that some groups aren't trying right now).
So find a good system. Have fun. Keep the books. If there are too many books to carry then sure, supplement your load with PDF versions. Just make sure you are willing to lose them when all is said and done. The way things are going in the entertainment industry, non-digital books may be the only items you can truly claim ownership over in a few decades.
For me, the best system will always be Savage Worlds. With one small book and my imagination, I can do anything.