I've tried (old) Afternic - new ownership now. WhyPark, Fabulous, TrafficZ, SEDO, GoDaddy & a couple others. I now use a very simple customizable template - keyword, SEO'd script that I can just fly with. I've been offered a Parked account recently because I have large, keyword-rich portfolio. WhyPark enables you to use affiliate banners/scripts & Adsense, etc. So, they're good for that. It also depends on the specific "type" of domains you have. Different companies optimize different sorts of DNs differently. I've had the best return from Fabulous (overall) thus far (over 10 years of parking trials). For instance, Moniker/DomainSponsor is best for adult, TrafficZ is best for "brandable, non-dictionary; SEDO is too saturated for my taste; WhyPark is great if you don't want maintenance but don't want to fully develop a domain - but you still need to be smart about keywords, SEO, etc. with them & they work. GoDaddy is questionable & so is SEDO, IMO. Best be is to get your own content on every site - make sure it's NON-DUPLICATED!!!!!!!!! You don't have to "fully" develop a site - but in my opinion -you DO have to have SOME original content to even show up &/or be indexed by Google at all!!! Most important! With traditional parking pages such as what you reference, you NEVER show up in Google (or others), which renders you're site rather useless (especially for resale). You're always making others money - never benefitting yourself. Buyer (of the idea of parking) BEWARE! Most domainers with a couple to several (only) DNs don't usually make more than a couple of cents to dollars a month with the traditional services, no matter who they go with.
Oh! Also, as I was reading some old posts - part. those fr/ 2007 (things have changed since then dramatically) instead of driving traffic TO parked domain sites (usually against TOS) WHY DON'T YOU TRY to DRIVE TRAFFIC FROM a couple of "money sites" (fully developed, SEO'd DN sites) FROM your PARKED pages. You can only do this with a customizable, independent script or a BLOG or from (NOW) WhyPark. Not many "duplicated content" issues with them & they fixed all that recently. Cheers!
I'm using SEOParking .. but not helping my earnings .. currently I've parked about 15 domains there ..