VR and chant of vamp is the same thing but:
At lvl 30 (SO) you will have VR1.. which is nice. You need second class transfer to get it on WC.
At lvl 44 and 56 (SE) you will have vr2, vr3. At lvl 58(!) you will have CoV2... VR2 is good enough. BUT
w/ WC you get a lot more melee buffs namely:
haste2 (56),agility3(56, irrc),CoR62 (chant of revege, not so hot) (if you are DA you have it anyways).
W/ wc you lack WW and mana recharge but if you start a buff bot you won't have mana recharge untill you play it as main for some time (or you sub).
WC buffs costs a lot and cancel might trick you.
...
All in all I'd take WC any time.
Buff bots are single buffers, being a WC would be a huge mp waste because if something were to happen you got a while to wait before re-buff. SE on auto follow with VR and pop GSAP's is the best idea.