I have a Sigelei Zmax. Fantastic device, I love it a lot, I love the battery life, telescoping that allows me to run damn near any battery I please, performance, etc etc...
BUT
I still use the heck outta my Smoov Rev/Twist clone. There is nothing wrong with them, IMO, as a toe dipper into VV/VW. You can easily pick them up for somewhere between $15-$25.