I stopped putting any stock in RCP after their prolonged insistence that Romney was going to win, right up until the bitter end.
My dismissal of them is purely anecdotal, but there’s been like four or five races over time that I cared about where they were telling me one (comfortable, ultimately untrue or skewed) thing, and other sources and reality let me down by being correct.
As much as I hate their editorial content, I go with FiveThirtyEight.com for poll data. Their track record is pretty good.
The problem is that you don’t understand polling. The LV/RV number represents the sample size, which matters only in calculating the margin of error. (LV means they polled likely voters, RV means that they polled registered voters). A higher sample size should mean a smaller margin of error, not more actual voters. Conversely, a smaller sample size is going to mean a larger margin of error.
Most polls are going to give you a margin of error between 3 and 5 percent.
There is room for disagreement as to whether RV or LV will give you the most accurate results. Also look at the methodology as to whether they used only landlines or cell and landlines (more accurate as to younger voters).
Each poll has a separate error rate so using a weighted average doesn’t provide much more accuracy than not using one.