Answer 1

sql server is owned by microsoft
oracle is owned by oracle corp

sql server has easier syntax
oracle has more complex syntax

sql server runs on windows
oracle runs on wide variety of platforms

sql server uses t-sql as procedural lang
oracle uses pl/sql which is more complex

sql server has job scheduling via server agent
oracle has oracle scheduler

sql server has no bitmap indexes
oracle has bitmap indexes
...

I suggest you to start with sql server for cleaner syntax and easier work process.