All business decisions like this are about what level of abstraction is appropriate for us (today) and what level of specialization is conducive to our strategy[1] (today).
In some cases the infrastructure outsourcing question won't even be particularly important - a wash essentially regardless of the path taken (in the bigger picture of the enterprise's mission anyway). Other times, it'll be - effectively - paramount.
[1] Or current priorities, concerns, strengths, weaknesses, biases, pressures, risks, opportunities, competitors, etc.