Though I did the mistake of moving a few 500+ MB apps to SD, yes they were quick to transfer... just as slow at backing up to SD as before my tests.
One thing that is a hidden bonus... before, when I disabled saving cached images in a xposed module... there was considerable lag in showing album art from mp3 files. Now it is barely noticeable when scrolling at a fast pace. I had over 300MB of cached images before disabling android's built in feature. Now I can have my cake and eat it.
Since many are moving apps to SD, I recommend the fastest speed you can get, not the fastest you can afford.
remember write speeds will very, by burst mode and read/write verification, as with TI Backup. I would assume dumping data would be greater, just have no way to measure quantitatively, just seat of the trousers.
Here is a list of compatible ultra high speed SD cards.
PNY Elite 100MB/s (Able to get them in the UK, US is low availability)
Sandisk Extreme (Plus/Pro) 95MB/s
Toshiba Exceria 95MB/s
Lexar 633x 95MB/s