In my opinion Mark should go before Chapter as Mark could be said to be the completion of the second degree and Chapter COULD be said to be the completion of the third.However all degrees stand on their own and we have had other threads about Chapter completing the Third (or not) so I don't want to really go down there. Suffice to say that logically the Mark should go first.
I am in both Mark and Chapter and love them both. I don't know any MMM (Mark Master Masons) who dislike Chapter or HRA (Holy Royal Arch).
HRA is pushed more by some Grand Lodges (sounding a bit like Lauderdale now :P) due to the close association some Craft GL's have with HRA. In a lot of cases the Grand and Prov bosses of Craft are also head honcho's in HRA.
Basically, it's political, and historical. If you look at the formation of UGLE you will find that HRA was a big point.
My advice would be to, when you are ready, join Mark and then HRA. However I would say that as Mark is a much simpler order I would not wait a long time to join if I where keen.
HRA is a lot more complex and you would be wise to study the Craft first.
Above all Freemasonry is about enjoyment and you should do what feels right to you, and when...
Thanks,
Dave...