I run both Fedora Core 5 and Ubuntu 7.1.0 on two different machines
and they both work fine.
1. I mostly compile from sources and install in the standard
directories, i.e., /usr/local/. If you rely on package managers,
e.g., aptitude, apt, yum, rpm, then you are bound to get different
versions and different directory structures. Standardize on your
install structure and stay with it across the distros. This means
that you have to download the tarballs that you want and hand
compile. Well worth the effort in my opinion.
2. I mostly use Yum install which roughly parallels apt-get
installations. Rpm is at a much lower level and should only be used
if yum does not work. Having said that, try to install ruby,
rubygems, etc. from sources rather than the repositories and keep them
the same across both your Redhat and Ubuntu systems. You will find
that they work the same (to best of my knowledge). The more important
things are the supporting libraries for compilation and/or operation,
e.g., you need readline to support irb etc. The dev libraries need to
be installed to support compilation processes. They have some
variations across these systems and need to be researched. I did.
3. There was a thread in this forum where later versions of Fedora 8
(I believe) was causing memory leaks in ruby for someone. I think he
downgraded to Fedora 6. I have stayed with Fedora 5 since I don't
need the latest and greatest. Command line works the same across all
4. I had used Fedora, CentOS, and Redhat extensively before I came to
Ubuntu. It is just a matter of getting used to. Once again, if you
keep compiling from sources and keep the versions identical across the
linux distros, you will not notice any difference (at least I haven't
which has bothered me to the point where I can remember it).
5. Regarding desktop, I keep the default Gnome and really have not
noticed much of a difference except that Ubuntu is more polished.
Again, this is very subjective and I must admit, I am more of a
command line person than GUI user so these differences do not matter
much to me.
Hope this helps.