Mic, if you carb on CO2, then push with blend, it will lose carbonation over time because of partial pressures.
For example, I run my CO2 at 15psi. At 39F, this gives me 2.8 volumes of CO2. If I run 75/25 blend at 15 psi, the partial pressure of the CO2 is 25% of 15 psi, so it's effectively 3.5 psi giving me 1.7 volumes, and so over time the beer will lose carbonation, and seem flat.
Now for nitro pours this is a good thing. You need to run them at 25-30psi to get good flow thought the restrictor faucet, but you also want lower volumes. 28psi of 75/25 blend, has a CO2 partial pressure of 7psi, so that's 2 volumes, which is good for stouts.