I just started building up my blog network again. I use the free one's as the outer-layer to help with link building and some added traffic.
disclaimer: I'm not a reviewer, so I may be completely off basis and full of shit, these are just my limited experience with using these blogs for the past couple of weeks !!!
pornblogspace.com - pretty good speed, uses standard WP interface, has like 12 plug-ins and over 100 themes to choose from.
pornlog.co - good speed, has a limited set of the WP functions. No plug-ins that I can find. 25+ themes.
pornblog.me - can take a bit to get pages in the admin area to load at night. Limited set of WP functions and theme options.
vidpole.com - have had a couple of times that it seemed laggy when posting. only Akismet as a plug-in and 5 theme's. URL is not a sub-domain like yoursite.vidpole.com its vidpole.com/yoursite/ all the others are sub-domains, not sure if that makes any difference at all
easyxsites.com - good speed. seems to be a custom dashboard not based on WP. Nice traffic stats, but no plug-ins other than plugrush. Very limited theme's pretty much the same layout, just different colors. Looks like there is a premium area where you can edit the theme, but since I just started have not gone that route yet
mediamofo.com - very laggy at times
based on standard WP dashboard. 8 plug-ins. 15 themes. SEO plug-in by default.
xobler.com - good speed, couple of plug-ins including JW player and jetpack. Almost 50 themes.
Hope that helps
T.