If you've spent any time looking through your campaign's Advanced Settings options, you may have noticed a drop down selection for "Default Editor(WYSIWYG)". Under the current settings, Obsidian Portal defaults new campaigns to the CKEditor for use in building pages, but that's not your only option. You may also elect to use the Textile editor, which is the older, original editor that Obsidian Portal has had since it was created.
What's the difference in these editors?
On a basic level, not much. They both let you create and edit campaign pages. They both have toolbars that let you apply common text styling such as bold or italics. They both let you input material, and preview the results before saving. The differences come in how things are parsed, what code is inserted, and what features are available for each editor - and that's where you're going to want to look closely in order to make a decision. Do you want pressing the <Enter> key to be a return, or a new paragraph? Do you want to have to press a button to view your page's source, or it's preview? Do you prefer the more modern HTML markup, or the more simple textile markup? Do you need the slug insertion buttons, or not?
Ultimately, it's most likely going to be a matter of preference. After all, you can swap editors anytime you want. That said, it's strongly recommended that you do your experimenting with the editors early, and limit switching once you've made a choice - to avoid the differences that might crop up in pages as a result of the different parsing schemes and code insertion.
In the end, the right answer is yours.