I've had both. IV once, oral twice. Eyes improved with IVSM, no change with orals.
IV leaves a nasty taste in mouth, energy to spare (grocery shopped before lunch which is always after), I'm easy stick cause I exercise alot.
Orals give energy, took away my sudden spasm jolts while watching tv at night (the 1st time I took them anyway, the 2nd not as much & I get them all the time now),

I say it depends on the hit you want. I love neuros that let patients call their own shots since you know your bod more then any neuro.