I don't know Oracle at all but I have heard Oracle DBA's saying that working with Oracle (as a DBA) is "harder" and more difficult and more demanding than working with SQL Server. Does this statement have a basis?
Since Oracle has more configurations to do during setup/installation, this task it usually left to the Oracle DBA. SQL server is much easier to install for a windows server admin due to the similarities (Microsoft). This easy SQL installation process is also one of the greatest problems. The windows server admin pops in the DVD, installs SQL and thinks "These SQL DBAs don't do anything". Due to this kind of administration by non-DBAs, there are a lot of breakages in SQL server during production operations. This is what leads to the conclusion: Oracle is much stabler that SQL.
For Oracle, the server admin installs the OS and the Oracle DBA does the DB install. Two professionals required. For SQL server, sometimes the server admin gets excited and carries on with the SQL install (not a good practice). One professional used. This makes it look like Oracle is harder/complex than SQL server. Although the non-DBA who installed SQL will never take ownership when a problem arises and the solution to the SQL problem is not the first result in a google search.
Since Oracle is installed by an informed oracle DBA they can configure and administer it the way it should be. Thus giving an acceptable up-time and throughput. Meanwhile the SQL server has to choke on its own fragmented VLFs as the server admin put the data files, log file, and tempdb on the C drive with the OS and pagefile. This give the impression of an Oracle DBA working harder that a SQL server DBA.
Oracle DBAs have to be familiar with different OSes. I will give them the credit for that. But the basics of Oracle remains the same and so is the administration. I have administered Oracle on HP-UX and on Linux. There is a small learning curve to it, but that is the fun part of working in IT. Also the learning curve is basically for login and directory navigation and a few other basic commands. Once you get to the Oracle console (or fire up OEM), it is all the same regardless of OS. Please note that everything above is just my opinionated answer to the question asked.
Oracle has a significantly higher barrier to entry than SQL Server. Does that make working with Oracle "harder" than SQL Server, well that depends on what is meant by "harder" and where you're setting the bar.
I've very rarely encountered enterprise, Oracle backed systems, that didn't have dedicated Oracle DBAs/developers on the development team. I frequently work with SQL backed systems that have been developed without any DBA expertise whatsoever.
Microsoft are smart. They've built a database platform that competes with Oracle but made it accessible to anyone that can knock up a database in Access. The notion of Code First, for anything other than the most noddy of departmental applications, scares me witless. But doesn't it make great commercial sense?
Hide the complexity. Make it easy for anyone to build on your database platform. Later, once they're locked in, they can find all the knobs, levers and switches they'll need to get the best out of the product.
Oracle requires expertise on knobs, levers and switches before you can create your first table. To the novice, that makes Oracle more difficult to get started with. Not technically more challenging, just in comparison to SQL Server, plain difficult.
If you're a developer that just wants to "get things done", which platform are you likely to lean toward?
Is an expert Oracle DBA more expert than his SQL Server equivalent? No. Is Oracle technology more complex than SQL Server? No. Is difficult or demanding a good benchmark for anything? Commuting across London on the underground is both but I don't feel superior for doing so :)
Oracle has more features and options and many more configuration knobs and settings, so there is a lot more to know and manage. SQL Server has UI features that make a lot of tasks look very simple (some would say much too simple) and hide complexity from less experienced users. That probably makes the knowledge barrier to becoming a SQL Server DBA lower than for Oracle.
Also, Oracle is supported on a number of different OS platforms, wereas SQL Server DBAs only have to know about one OS.
On the other hand I've known DBAs who support both who have said that Oracle is much less trouble because it breaks less and doesn't need to be fixed as often as SQL Server.
SQL Server is easier to install for Windows admins - when they install an infrastructure product (eg Websense, VMWare's Virtual Centre, Symantec Endpoint Protection etc) that requires a database, they get the job done ever so quickly. And that's half the "trouble" with SQL Server - anyone can do it, and it'll work swimmingly well - until something goes wrong.
SQL Server also integrates well with the .net fraternity - so often you'll find database designs done by c sharp developers rather than dedicated database developers. This isn't a recipe for scalability.
A badly written application will perform badly on both Oracle and SQL Server...