I prefer Marlowe - I love the look, sound and associations with writing. I like the idea of Merritt but I know someone with the name; she’s lovely but her name sounds screechy in my accent. My sense is that itt sounds & works much nicer in rhotic accents.
Vibes:
Marlowe - British, artsy, bookish and hip, warm and a little unpredictable.
Merritt - American, southern belle, studious, head cheerleader, bright and effective.
…thinking I may prefer both as middle names.