I’m partial to 4A, especially if its an early morning of late night flight when I’ll want to sleep, as 4A allows me to recline without guilt. That being said, the E175 might be the only plane where I don’t mind the bulkhead. There’s plenty of legroom and the smaller bins right above your head are large enough to hold a laptop bag. If it’s a meal flight and you want to ensure your first choice, I might lean towards 1A. In my experience flight attendants always take orders front to back on Delta Connection flights regardless of flight number.