and Manhattan have great respect for each other in terms of their quality. Honestly, I'm less familiar with what Manhattan has to offer, as they are smaller, but given the fact that the founders of Veritas
respect what they're doing says a lot. Additionally, I've heard good feedback from their students.
Your second question is more of an individual nature. It sounds like you want to take an online course. To be honest I think these are of less value than in-class sessions, so I would spend some time with The Tenth Edition for GMAT Review and other less expensive resources to see how you perform before splurging on an online course.