depends on your purpose
1) the SE has a much better graphics card and hence is suited for gaming. it can be overclocked also to a nice degree. the 5521 has also a reasonable gpu but it is lower than the special edition. for reference you can check notebookcheck which gives a score of 1500 to 8730m and 1700 for 7730m.
2) the dell 5521 has a ulv processor which saves battery and hence gives you very good battery life. its an ultrabook processor. however it is at least as powerful ( source cpumark ) as the i5 hence the dell 5521 has a superior processor
in conclusion the 5521 seems to be a better choice for superior battery life and more or less same frames in games as the special edition ( a little lower , 12% decrease). you can overclock to compensate.