The knock against coulter systems is when the soil is dry and compacted, coulters have a hard time attaining and maintaining depth. If you're going to be creating strips in fairly moist and mellow soils, a coulter setup is fine.

There are lots of fantastical claims with banded fertilizer so I would urge caution when weighing these claims. A 15 to 25 bu. yield increase is certainly possible, but in my experience i have only seen that kind of increase in soils with poor fertility. If you have maintained your soil fertility at good levels, you probably won't see much of a yield bump over broadcast applications.

Also be cautious about claims of "increased efficiency" when using reduced amounts of fertilizer in a band. Banding does not decrease the amount of nutrient the plant needs to produce a bushel of corn. What it does do is increase the amount of applied fertilizer that is available to the crop, which increases yields if your soil can't supply enough nutrient (ie. low testing soils) when the plant needs it. It's important to note that if you apply less nutrient than the plant removes, your soil test values will fall.