They are very similar! So I think I would be tempted to go for the less ££ option. There are a lot of people on here who have zatchels satchels so hopefully they can come and advise.
I have a zatchels saddle bag and have been pleased with the quality. I haven't kept any satchels as found them too small inside.
I also think the zatchels one is probably not as bright in the flesh - looks like flash bouncing off it making it look bright.
But just reading your OP again you say you love the Cambridge one - so you should go for that one.
Not very helpful, am I? 