Is your Question directed at the usage in Stompy, or in general? Because this depends heavily on the deck and Manabase you are playing, and on the Situation in the game. In Stompy, of Course you always grab a Basic, because most lists play Fetches only to trigger Narnam Renegade.
There are a few exceptions that utilize Temple Garden for a White Splash, in this case you would Always get the Shock land as soon as possible, since your Options of deck Manipulation and ensuring you have the Right mana available are limited.
This depends also on your personal preferences, but I agree with phaircaron, more than 4 Evolvers can make for strange starts, where you Play only 1/1s without an early possibility to make them bigger.
And in the direct comparison, Ex1 is definitely the winner for me, since I think Regeneration is more important than Trample, and 2 counters is much more easy to accomplish than 3 (in fact, most of the time the Ex1 will be dead before the second counter).
Personally, I Play 4 Experiments, 4 Dryads (agree with Phaircaron again, they are crucial in the curent meta) and 3 Renegades.
There will definitely be no Reprint of the Fetchlands in Horizons. A Kind of replacement is possible, but I think its not very likely.
Investing in the Fetches (to Play with them, of Course, not as a monetary Investment!) sounds like a reasonable choice to me. No guarantees that they will maintain their value, but since they are relevant in all eternal Formats, they are not likely to loose much of value.
And if you plan to get the Fetches for Stompy, you can start with Wooded Foothills and Windswept Heath, which are the cheapest Fetches you will find.