What are you looking for, 2.4 Ghz or FM?
Futaba has over 17 years of history with 2.4 Ghz in
comercial applications before using it in hobby radios.
I have owned JR and Futaba radio equipment and have had good
results with both brands as FM radios.
Was out of the hobby for awhile, when I got back into it I did some
research and found Futaba had the fewest issues with 2.4Ghz so
I went with that.
I think most issues are with human / user error than equipment problems.
Spektrum is I think aligned with JR.
I would go with what ever equipment has the features you are likely to use.
I also had warranty work (broken antenna) by Hobby Services for my Futaba
was quick and no hassles.
As to who sells the most? I can't say.
Happy flyin', Oscar