SVN in Eclipse is spread into two camps. The SVN people have developed a plugin called Subclipse. The Eclipse people have a plugin called Subversive. Broadly speaking they both do the same things. What are the advantages and disadvantages of each?
Both are very similar but Subversive is the "eclipse svn provider". I primarily use Subversive because of a few convenient features:
Grouping of history
When I'm browsing the history of a branch instead of just seeing a bunch of rows for every commit it can group commits by today, week, etc.
Mapping of trunk, branches, and tags
Subversive assumes the default svn layout: trunk, branches, tags (which you can change), so whenever you want to tag or branch it is one click and you provide the name of the tag or branch.
Like I said these are minor differences that I just find convenient. Both work great with mylyn, but overall there really isn't a whole lot of differences with these two extensions.
Merging with Subversive is a pain though (haven't tried Subclipse), I've never been able to successfully merge. The preview of the merge is great but it would never complete the merge or it will take way to long. Most of the time I complete merging through the command line without any issues.
With every new version of Eclipse, I install Subversive, because it's the standard provided by Eclipse. And every time, it has issues recognizing my pre-existing projects.
So I end up uninstalling Subversive and installing Subclipse instead, which works marvellously. I also frequently use SVN from the command line as well as in Eclipse, and Subclipse has no problems with this.
I have just discovered that I cannot figure out how to view a properties diff with Subclipse. In Subversive you select two revisions in the history view, right-click and select compare properties from the popup. This is enough for me to stick with Subversive.
The reason for trying to switch was Subversive's strange behavior on OS X: Some automatic operation called 'svn cache update' hogged the CPU at abnormal levels after every 'svn update' run, always taking an annoyingly long time to complete.
I had the same problem as some others even getting Subversive to work, so I can't say if it's better than Subclipse.
Subclipse is really lacking when it comes to integration with Eclipse for tags and branches. You can do them, but it's nowhere near as seamless as it is with CVS.