Eagle is horrible to use, and not really free, it's free in the sense of "free advertising" for CadSoft
Clearly the best free software for a beginner is Kicad. It still has some rough edges, but is capable of professional quality production. With support from CERN, it can only get better.
this is one place this forum would benefit from thumbs up.
the OP asked 'best for a beginner' and then went on to add something about incorporating chassis.
Eagle has been around for a long-long time. DOS era ?
HUGE base of users. That means two things. first is there is a source for answers, second, there is a lot of shared files for people. the outline and pinout for the Arduino UNO footprint allows one a starting point. Also, Eagle is used professionally. so, if you are going to be a design engineer, knowing Eagle is a huge plus on the resumé.
the learning curve is often called a sheer cliff or a block wall. This thread has a fellow who said weeks at 3-4 hours a day and I can assume that at that rate, he is only becoming proficient.
I think I have only seen one other person say they use WinQCad.
good start, but it is unfinished and the writer abandoned it. I had an unlimited license, but a computer crash has left me with the free version. based on support and users, it is NOT recommended. Has come VERY klunky parts. And is really multiple individual programs. Seems to have been started in DOS and truly has not become a windows program.
as you probably know, almost all the free stuff has limitations. either number of pins allowed, board size or some other arbitrary wall. you can buy your way into a larger version, but that commitment locks you into a path that may not be the best in the long term.
try each of the versions out there. some are free to try, others have limitations.
if you are a hobbyist, find the one you like best and using my experience, burn a copy to CD for posterity
I love the autoroute feature. not sure if all the freeware has autoroute. as a note WinQCad autoroute is klunky. you lay out locations, then autoroute and then move your traces as you want, but cannot autoroute a second time.
I see fritzrig as an upstart that has a lot of followers of the students. this means a growing users base that will be a force in the future. In my mind that makes it more mainstream.
Eagle PCB over 3 million hits
friting over 300,000