I would be inclined to go with TPS.
As it allows for investigation of all participants interaction with systems.
You could easily create a data flow diagram of a system.
How different systems process-- e.g. web-based, batch files, real time, etc.
How information is stored on different media and backup schedules-- i.e. grandfather son, etc.
Recovery methods.
Investigation into decision support-- really helpful if you are considering IT later on.
How technology is deskilling-- also the loss of jobs.
Is the system collecting bias information.
Quality,integrity and security of data.
Databases: mostly focus on flatfile, primary keys, schemas, relationships(one to many, etc), differences between paper-based an electronic, data dictionaries, types such as (text, number, etc and validation rules), DBMS, SQL, storyboards and associated issues.
When I was doing IPT my teacher taught Databases and seeing as we still had time left over we were taught part of TPS.
Essentially have a look at the syllabus and see what you think-- as ultimately it will be you who has to sit the exam at the end of the day!
GOOD LUCK!!!