If you only delete the files from your Mac via Finder, but leave them listed in the Apps part of your iTunes library, then they will not be copied back from your iPad when you sync again (unless there is a newer version on it).
If you do have to restore to a backup at any point in the future then to restore to an iTunes backup you will need the apps on your computer (a backup does not contain the actual apps, just their content/settings), and you may not be able to redownload them from the store (e.g. if the developer has removed them). An iCloud backup also doesn't contain your apps, it will redownload what it can from the store.