The first thing is there is an extremely important causation effect, the more investors you have, the easier it is to get more people to invest (social proof).
So, inbound vs outbound:
If you have a lot more investors already committed, you have a lot more social proof. Naturally if you have more investors, you will have a lot investors talking about your deal to other investors. Thus, the people who contact you inbound want to invest. However, it has nothing to do with the fact that they are inbound, it is just that by the time they are contacting you, your fundraising already was dripping with social proof.
Conversely, at the beginning when you have no investors, you likely are going to have to contact some of them. This is obviously going to have a much lower conversion rate, because you have no social proof!
Taken to the logical extreme, if inbound investors are so much more valuable than outbound, when you start fundraising you should just sit next to your telephone and wait for investors to call you. But of course that won't work, because it isn't inbound investors that actually matter. It is all about building social proof, and then once you have that, a lot of good things are going to happen. For example, YC is very powerful indication of social proof, and look how much easier fundraising became!
Basically, people who read this TC article: if you are interested in fundraising, PG wrote the canonical piece about it, http://paulgraham.com/fr.html
This post is fun, and I congratulate you on raising your round, but this data isn't predictive or useful.