Having stayed at both Diani Sea Resort and Amani Tiwi Beach Resort, my vote would be Tiwi. The hotel is about to reopen after a devastating fire, we stayed in January of this year in the midst of the construction and the hotel will be stunning, the rooms are bigger with a separate dressing area and then air conditioning much more efficient. The staff at Tiwi are just more attentive and efficent. There are no other large hotels on Tiwi beach so there are fewer beach boys to hassle you, the hotel does have an area of beach with sun beds on and on which no beach boys are allowed, you can also choose to eat at restaurants situated on the beach. Amani Tiwi Beach is some distance to any where, though the hotel does run a mini bus into Diani the shops and bank - there is a charge for this. If you like to swim in the sea you will need rubber shoes because of the coral, though this does mean there is excellent rock pooling opportunities and just a short walk away there is a perfect sandy place to swim but please ask the staff about safe swimming times as this stretch of beach is very close to a river estuary.
The pool at Amani Tiwi Beach Resort is huge with a verity of water depths and a swim up bar. The pool at Diani Sea Resort is tiny in comparison and doesn't have the swim up bar. Because the pool area is so large at ATBR it is always possible to find some where quiet to put your sun bed while it is definately 'cosy' around the pool at DSR.
Don't get me wrong there is nothing wrong with Diani Sea Resort and it does have the advantage of being able to walk to local shops, bars and restaurants. They don't have sun beds on the beach as the sea comes up to the hotel sea wall at high tide. The beach outside the
hotel is beautiful and although there are loads of beach boys the security staff at the hotel are good at intervening if they notice hotel guests being unduly hassled.
If you want peace quiet, good food and to be treated just a little bit special then choose Amani Tiwi Beach Resort. If you like to be closer to other hotels and like good honest value for money chose Diani Sea Resort.
No matter which hotel you chose, please do go out and about, Kenya is a beautifu and diverse country which deserves to be explored.
We are going back to Tiwi at the end of January, so if you chose Tiwi early February we might well meet up - I can' wait:)