I'd go with NameCheap simply because I've never had any issues with transferring domains in/out from them. I was in a situation with GoDaddy where they would not let me transfer one of my domains out for almost half a year due to their "terms". They seem to have a lot of tricks up their sleeves to force you to keep your domain with them. Not sure if it's still in effect, but the last time I was with them you were not allowed to transfer or unlock your domain if you recently made a change to any of the WHOIS details within the last 60 days.
There are many domain providers that you could sign up with. I like to use and tell people about name cheap. Sometimes you may run into some wonderful deals or promotions when visiting their site you should really check them out. Also don't go with godaddy they aren't as that good as everyone things they are.
I would only use Namecheap or Godaddy after a terrible experience with my very first website. I bought from a fly-by-night kiddy host without realising it at the time because their website looked as professional as any other I saw. About 5 or 6 months later my site went down all of a sudden and it transpired that he actually registered it in his own name and then sold it on to someone and I had no way of proving it as the only proof I had was an email receipt from his sham hosting company. I went nuts at the registrar who wasn't any help at all and said "how was I supposed to know he didn't register it properly"? He said "you should never ever buy anything from a reseller". I didn't even know how to tell the difference back then but he said stick with Namecheap or Godaddy and you'll be fine.
I just never expected such a thing could happen and have no legal recourse. Little did I realise it's par for the course in the industry lol
As you don't want to do it with Godaddy and Namecheap seems to have high praise I'd go with them.
i have bean using dynadot for many years and had more than 15 domains, never got a problem by transfer a domain to other domain registry site and they are stable, they transfer within 2 days after transfer requested! so i recommend to use dynadot.com