I am familiar with BTCPop, BTCJam, and Bitlendingclub (BLC). I love the concept of peer to peer lending as a way of disrupting traditional banking, and I love bitcoin. The two ideas work beautifully together - although unfortunately I don't think any company out there is doing it right yet. For example, loans are supposed to be tied to an interest rate, so that the sooner you repay the less interest you pay. This occurs with all traditional commercial debt, from mortgages to car loans to credit cards. All the bitcoin platforms, on the other hand, only calculate the debt over the term of the loan as a lump sum, so if you pay late or early it doesn't matter - you pay the same interest. So, for just one example, it makes no sense to refinance any debt to a lower interest rate. I'm hoping they do away with that soon or a competitor pops up which does. Peer to peer lending thrives on markets and it needs those options to be there.
BLC is the best of what is out there, in my opinion.
BTCJam is the largest platform so far, and the interface is nicer. They also have the market to sell notes for active loans, which is good. It allows a quick profit turnaround or ability for people to buy up defaulted debt to collect on it. However they seem to be doing everything they can to drive away legitimate borrowers. A few gripes in no random order:
1) bad customer service - check out the threads in
https://btcjam.uservoice.com/forums/175861-general and see for yourself. Many of these ideas are completely ignored by management. Even worse, some of them are responded to as being high priority and yet no action has been taken on them for over a year.
2) They take their cut out as soon as the loan funds. This incentivizes volume in getting loans funded without emphasis on people who actually repay. BLC on the other hand, takes a cut each time someone makes a payment so their incentive is right in line with keeping defaults low.
3) Their recent changes are all changes for the worse, in my opinion. For example, they fix the interest rate based on their in-house credit scoring. As a lender, I can't ask for more for someone I find is higher risk, and as a borrower I can't ask for less. BLC uses a market mechanism to find the interest rate - and since markets are the principle behind which p2p lending works, that just makes more sense... BLC isn't immune from this (they recently capped their loan terms to 270 days to help prevent defaults) but overall BTCJam just seems to me to be continually dis-improving.
BLC on the other hand has the interest rate price discovery mechanism, which I think is the best format for a loan market. If they added in the flexible loan terms and real APR interest amortization it would be perfect. They also seem to be taking more efforts to stop scammers and are WAY more responsive to customer feedback. You can post on their forums and the CEO usually responds within a day or so. Much better, in my opinion, and more importantly - they look like they are on the right track to getting better rather than getting worse.
BTCpop is good - I like their innovation of a default insurance to help prevent loss, but so far they are way to small to operate. They only have active 31 listings at the time of this posting, for example. I also don't like that you have to register for an account in order to browse the listings. It makes it look like they are hiding something.
For all of them, there are no legitimate bitcoin collection agencies, and as far as I am aware no defaulted loans have ever been successfully collected on by outside companies. This means you are gambling to an extent on the loans you fund. I'm in the game until the day that collection companies arise - then I think it will go more mainstream.
Your best bet if you want to see the difference between the platforms is simply to start using all of them and see which you prefer. That's the best way, in my opinion. If you are willing, you can use this link (
https://bitlendingclub.com/invite/aqorlx) to sign up the BLC account - its a referral link so I will get a scant 0.2% of any loan you take out. Good luck! Let me know if you have any other questions.