Both can be great. A true bookshelf speaker is designed to be placed in a tight space while many good monitors will sound best on a stand several feet from any wall. Most bookshelf speakers are not ported/vented, some may be front ported. Most bookshelf speakers will lack some bass due to size and placement.
So, where do you plan on placing your choice? If you plan to use stands, consider some floorstanders also. Don't think of putting rear ported speakers on a bookshelf.
So, where do you plan on placing your choice? If you plan to use stands, consider some floorstanders also. Don't think of putting rear ported speakers on a bookshelf.