My understanding is that internal memory is likely to be muuuuch faster than any microSD card, both in terms of low latency (how long it takes to locate and access a particular piece of stored data)
and in high bandwidth (how long it takes to read or write large areas of storage)
The new Android 4.3 version in Note 3 is the first Android OS with automatic TRIM
support. That will prevent the degradation of internal memory speed over time, but I'm not sure if that advantage also applies to a microSD card.
As usual, EarlyMon feel free to expand on or correct any of the above!