This will do "subject contains Some or search or text" while, as you've found, wrapping the string in double-quotes will do "subject contains Some search text".
You can save yourself a click by typing subject:"Some search text" and hitting Return to do the same thing, or from:nige_s@example.com to find emails I sent from that address, etc.
Or maybe you want to find that email from me where I thanked you for this Mail tip? Use a boolean in the search: from:nige_s@example.com AND subject:Thanks