Both are 10%, that is why percentages are percentages and not just hard numbers.
With cruise only rates, packages, differences in OBC, refundable, non refundable, free this, free that.. the best thing to do is make your own notes. Write it down in a spreadsheet, a notebook and run the numbers.
We book with one US based travel agent most of the time because they are cheaper and have better conditions. We've booked through Dutch, British and US based companies over the years.
We now stick to one company/TA, we book through their website and one of the familiar names of their team will get in touch.
The one thing I haven't found yet is that wonderfull travel agent that is the cheapest, gives a ton of onboard credit and who keeps an eye on pricedrops, calls me up about those (rather not due to timezones LOL ) and gets me an upper suite for the price of an guarantee inside, with a big flower arrangement and the captain carrying my luggage. I know they excists! Because people rave about them, although in smaller ways then above of course.
What I don't believe is that such a personal TA is the cheapest at the bottom line.
I tend to think I am a Smart cruiser, by booking not with a too big or too small company, which gives me enough credit showed up front, has a user friendly site and good response to requests. The prices match the cruise line websites rates but with extra credit.
After booking I check a few times for a price drop through a mock booking and request a change to the booking, depending on the conditions.
That is my best practice experience.