Lots of interesting information in this thread.

Personally there are 2 points that stick in my mind on 30" planted beans vs 15" splitter beans:

1) as Dave mentioned above, with a dedicated 12R30 corn planter you are not dragging around 11 or 12 unused boat-anchor rows when planting early corn in often wet conditions.

2) planted 30" beans will often canopy very close to 15" beans planted the same day IF you choose the correct variety for your area and row spacing. For 30" choose a taller, bushier bean. DO NOT plant the same short upright bean variety you would drill at narrower spacing!

If corn is your primary cash crop as it tends to be in central Indiana, equip yourself with a planter focused on corn.  You can plant beans with the setup you choose for corn. Beans are a lot less finicky to plant than corn.  Beans do however reward you for the good job of seed planting, depth control and seed to soil contact in a cleared warmer row that you can do best with a 30" planter.