Best gaming consoles similar to Nintendo 3DS?

I am looking to buy a small handheld gaming console and have no clue which brands are good or whether to just buy an old real Nintendo 3DS. I heard of AYN, Retroid, and Anbernic. I just wanted to buy some console for nostalgia, but there are too many versions and some say one is better, others say the opposite. If you could, please recommend some consoles (the budget is not a priority) and your personal experience with them. Thanks!