I honestly have no clue. I mainly only use two and both give me an upvote along with a resteem and are cheap enough that if they don't give any results then its no big deal. @resteemr is one that I use and cost just 0.01. I think its manual resteems as they can take a couple days to receive after payment. They other service is a free resteem bot that also offers a paid for subscription ( 14 resteems ) for just 0.10. If you use his free service you have to visit / post in his topic daily. The paid for options lets you keep your MANA and Resource credits you would have other-wise spent commenting daily. Well worth the 0.10 fee I think.
Dang I just got the out of RC message ... I am lucky that I joined this place when I did. It will be very very difficult to grow as a complete newbie using this new RC system.