I won't post directly about different payment processors, but I will cover something that most think about at least at some level.
As with most things on the internet, there are concerns about identity theft, access to bank accounts, and thievery of funds from your payment processors. It's very important to protect yourself in every way that you can while doing anything on the internet.
With my expertise in desktop support and security, I'll talk about some things you can do to protect yourself. Although it would be wise for me to just copy/paste from an e-book I wrote a couple months ago that contained this information, I'll post it here without including links hand written once again.
From a personal protection point of view, excluding things you should do for yourself such as due diligence on any payment processor of choice, there are things you should do to protect yourself while on the internet in its entirety.
1. Frequently search and clean adware/spyware from your PC. There are 2 free products that I use in my PC repair business every day. "Ad Aware" and "Spybot - Search and Destroy" can both be found at
http://www.download.comDownload both, update, and run individually and clean what they find.
Why run 2 different scans?
Although both do a fine job, I've found that Ad Aware finds different things than Spybot does, and visa versa as well as finding a lot of the same things (thus why you should run them individually instead of at the same time).
2. Get a good anti-virus software. When I say "good", I don't mean AVG Free Edition, Norton, or McAfee.. I mean, find a good one that makes you feel comfortable on the internet. Personally, I prefer Kaspersky. It's what I've found that makes me feel secure on the internet and what I recommend to all of my clients. I was so happy with them, that I setup as a reseller with them as my first anti-virus software product. I'd never setup with another, because I hated recommending them.
3. If you are on a broadband connection without a firewall, get one. There are software firewalls that you can purchase, some included in good anti-virus product packages, but I prefer a hardware firewall. These can be found in a variety of stores in the $50.00 range. They not only protect you from outside intrusion (excluding trojans and other viruses), a hardware firewall will allow you to have multiple systems on the same internet connection (Internet Sharing).
4. Roboform - This is an excellent product for password management. It's encrypted and easily used by even an internet novice. Keyloggers are one of the primary tools that is used to gain usernames and passwords. This product will place this information into the form without any keystrokes alleviating the concern of a keylogger logging this information and sending it to it's creator/user

Roboform also has a password generation utility built in. You want to try to have different passwords for different sites. And, I don't mean like "password123", "password124", etc... Make the hackers work for it with a password like "H4n#!32NT8xxT20" that the utility can create for you.
If you run some of these scans and find that you have loads of adware/spyware on your PC, I suggest changing all your passwords. Pertinent passwords first (bank accts, payment processors, etc. anything attached to YOUR money), then move on to the others.
Also, NEVER fall for the e-mails from payment processors.
NEVER NEVER. If you receive an e-mail from your payment processor, don't click the links. Open your browser, login to the site and check things out for yourself. Although these e-mails appear to be from your PP, they're usually NOT. Be safe not sorry. It's easy to manipulate links to lead the unsuspecting into 0.00 balances.
Good Luck, I hope this contribution is worthwhile to this community.
-James Oliver