Sick to me is a way better link building tool. The only thing that senuke beats it in is web 2.0 creation. The nice thing about Sick is that the user community can code it to be able to place links on various platforms. Sick is such a nice tool because if you use it right you can get really nice link diversity, or target higher value links (more d0foll0w platforms and such). One aspect of Sick makes it so that you target less spammed platforms.
Sick by itself however is not the greatest, in fact without some of the better addons (called templates), Sick kinda sucks. Using Sick effectively requires that you purchase templates (to place a link on a specific platform such as for forum profiles, or even web 2.0, Pligg bookmarking site, etc) or code them yourself. You can purchase most of these for 2 months worth of senukex. You also need to have some knowledge of scraping URLs; the reason is that while you may be able to purchase templates to place a link on a specific platform you need targets to actually place the link on. The nice thing is that when you scrape your own target list, those sites are less likely to be spammed than the set of sites that come built into senukex. If you work on your lists you can have fairly large lists of targets for various platforms, which will ultimately allow you to build links on many more domains than senukex can. Obviously the price differential is a nice advantage of Sick (even if you have to pay for templates).
The biggest con to Sick is that it takes a bit of intelligence and a fair amount of time to build yourself a quality list of sites that you can place links on (think of it like AMR but with tons of different platforms). Senukex is very easy to get going out of the box and only takes a little while to get a campaign running. Senukex is more expensive but that is what you pay for something that works out of the box.
Just my 2 cents