For entry-level, go with MS SQL. Not that it's a better system, just that I think it's a better bet for somebody in your (presumable) position. Here's why:
As others have pointed out, SQL is a language. You probably mean Microsoft's annoyingly-named Microsoft SQL Server (2xxx) which is not a server but an application (a database engine) with deep server hooks which runs on Microsoft Server (2xxx), a server OS. Ugh.
So MS SQL and Oracle (which runs on various server OSs) are two database engines which can host your database instances, which is wehere the interesting part of database operations begins.
SQL is implemented differently inOracle and MS SQL, but it remains the same language. Think of the two as different dialects.
For job prospects, I would say that MS SQL is more likely to be productive (meaning get you a job) for an entry-level applicant, which it sounds like you would be. Not only is it more common, but the educational resources are far easier to come by. Oracle may (or may not anymore, things are changing) be more used in big-iron, Fortune 500 situations, but MS SQL can commonly be seen powering the inventory needs of a local chain or even a large individual store. Don;t get me wrong, MS SQL can scale up to ridiculously large just as well as Oracle (to my eye), but you are asking about differences, not similarities. You won't find many small shops running Oracle, and maybe not even medium (regional). SO while Oracle is a great and robust product with a lot of features missing* from MS SQL, so does MS SQL have a larger installed base and the most modern accessorized SQL, called "T-SQL" (Google that for a LOT more information). Both of these make me view Oracle as a great option for somebody who already knows a bit about SQL itself and the issues which arise in trying make databases actually work for the company and the customers, not just theoretically in the classroom SQL sense. This is where the actual Server OS and the middle ground of DBA work makes its real money.
See, anybody can get good at SQL, but making the SQL translate into satisfaction means dealing with the rest of the system. This skill set is better developed in a single-vendor environment with the massive educational resources available to Microsoft practitioners. Later on I would recommend learning Oracle as an extension of your solid skill base.
So, the two systems are not exclusive, but easily support a progression in learning. You can do it either way, but I think that the MS SQL route will yield better results early on.
*Both languages have progressed much, but some of the more praiseworthy special features are more common in the installed base of legacy versions of Oracle.