Traveling alone, second week of September, after a week in Barcelona, then a week in Sitges... trying to figure out which island to visit for 4/5 days. Menorca vs Mallorca?

Looking for chill on or near a pretty beach with that gorgeous turquoise water. When not at the beach a charming village to have breakfast or dinners that isn't overrun by tourists. Not big on staying at resorts, and prefer guest houses, or B&Bs.

Torn with staying in the village and visit the beaches? I guess I would have to rent a car... and worry about parking in town, but prefer not to. Mallorca might have better bus transport, but then probably to the busy beaches which I'd prefer not to visit.

Read about Ciutadella in Menorca that sounds lovely. Or Palma in the old town also sounds lovely.

Afterwards will fly to Madrid, then possibly onwards to Portugal and London and home.

Thanks for your experience and suggestions. Your guidance and direction is very much appreciated.

Palma is the capital city of Mallorca so is not some quaint part of an old town. It is however, my favourite city in Spain but it's not the quiet, relaxed place you seem to be looking for. The mountain village of Deia is very serence and quiet and close to a number of sheltered coves and beaches that take some effort to get to but also means that the likelihood of them being busy is more remote.

The south western part of the island contains some of the best, unspoilt beaches. There are a number of towns and villages dotted around this part of the island, often appearing quite sleepy except on market days. Having a car is a must, it's an excellent place to drive even during the peak seasons. Unfortunately I cannot advise you on any accommodation queries as we own two weeks at the Marriott Vacation Club there so that is where we always stay.

I haven't been to Menorca so cannot offer any advice.

Yes, Deią is pretty and very quiet. And beautifully located in the Serra de Tramuntana.
The Deią beaches are not very attractive, coarse sand and pebbles. Port de Sóller has a nicer beach but can get extremely crowded.
SE Mallorca has a lot of small coves with blue water and sandy beaches. Check the area around Felanitx (Cala Sa Nau, Cala Ferrera, Cala Marsal, Cala Brafi, etc. ...). We just spent two weeks in Cala Ferrera.

Haven't been to Menorca.

These two islands, along with Ibiza are all very busy in the summer. Menorca is slightly less so but Ciutadella is a busy place. Having said that, the islands get a bad name for the party scene on Mallorca and Ibiza, which is though, confined to relatively small areas. If you choose Mallorca, head to Puerto Pollenca. Not too busy once Europe's kids have gone back to school and it's in an area with lots of choice for restaurants and hotels and few all night clubs. The beach is lovely and the town of Pollenca, some 2/3 miles inland is my favourite place on the island.

Menorca has lots of good beaches and restaurants. Check out Cala Galdana for hotels, beach and places to eat. There's also Binibeca or Fornells offering nice beaches and close to amenities.