Hi D.,
I live in Long Beach only a few blocks from the beach. Sure, Manhattan Beach, Seal Beach & Huntington are beautiful BUT very $$$ if you want to be walking distance to the beach! If you can afford it, would be nice to be right there. There is also a main difference with those beaches to consider - there are big waves, there is no break wall, known for surfing. Long Beach has a break wall - it's waaaaay out there but it does cut down on the waves. My kids are 2 & 5 years so we actually prefer the calmer waters. Yes, the water quaility is going to be lower because of less circulation. When we feel up to being on guard & helping the kids with rougher water, we just hop over to Seal Beach.
Long Beach really has a lot to offer, especially for families. There is a beach called "Mother's beach" that is very calm, also walking distance from us & very safe for little ones. We can also walk to many restuarants, shops, library, bank, post office, fire station... it's a very nice community & much more affordable than the other beaches mentioned. There are also a lot of community events. We just had free breakfast at the park with face painting yesterday & saw many of our neighbors there - also walking distance. Christmas parade, halloween parade, free concerts in the Summer & movies on the beach. My kids also love the Aquarium of the Pacific which is 3 miles away. A membership there is very reasonable.
Check out our neighborhood at: http://www.belmontshore.org/
Also, if you need help finding a place to rent or buy, my husband's website is http://www.davemonty.com/ He's very familiar with all of the areas mentioned We used to live 1 block from Manhattan Beach & moved down here because it was much more affordable.
I just had to stick up for LB because we love it! Feel free to msg me if you want any more info. -M.