On this occasion I don't know the answer to the question: does the choice of compost you plant an indoor plant in really matter? My suspicion is it matters less than some people think...
The houseplant advice forum I've linked to on the right certainly thinks it matters. Every other "my plant is dying" thread seems to include someone making very precise compost formula recommendations.
We have change compost supplier several times in my thirteen year tenure at Stewarts, The main reason has been to find one that successfully eradicates the need to use chemicals to prevent bugs living in the soil. The consistency of the different types has varied greatly, from light and peaty to heavy and soily. We tend to prefer the former, as we have to lift it all day.
One important facet that is often mentioned for houseplant compost is good drainage properties, and this is usually used to justify adding grit to the mix. While I agree that with most houseplants good drainage is a must, I suspect this is less important in commercial applications as we invariably use sealed planters, so have to water with great care in any case.
I was always told that the nutrients in compost are exhausted after three months at most, so again this can't be a reason to favour one type of compost.
Finally, if growing media choice is so important, why is it perfectly possible (in fact some would argue preferable - that's another can of worms entirely) to grow houseplants hydroponically, i.e. in no soil at all? Technically speaking, the roots in hydro planters adapt to their position either above or below water, and empirically I've found that roots in soil adapt to how wet they are habitually kept, which again makes me ask: does it really matter what they are grown in?
Answers by email please!