Depends on the SOC. Obviouly, the higher capacity bank will accept more charging
The 10% is a rule-of-thumb for flooded lead-acid batteries.
It is predicated on the fact that a FLA battery
at 50% SOC will only accept 10-15% of its rated capacity (C/10 - C/15) in charging amperage so long as the voltage is limited to the normal acceptance charge, i.e., 14.4-14.8VDC.
Will smaller capacity chargers fully charge your batteries? Yes, of course, it just takes longer.
Will larger capacity chargers fully charge your batteries faster? Not necessarily.
Here's the rule: so long as charging voltage is controlled within recommended levels, a lead-acid battery will accept a given level of charging amperage no matter the size of the charger.
Say, for example, it's now accepting 15A with a 20A capacity charger (@ 14.6VDC). How much amperage will it accept with a battery charger five times as large, i.e., a 100A capacity charger?
The answer is, 15A. That's right, the larger capacity charger will NOT charge the battery any faster than the smaller one, so long as the smaller one is capable of furnishing all the amperage the battery will accept at any given state-of-charge.
Can you have too small a battery charger? Yes, of course, but not because it's incapable of fully charging your batteries but because it's just too inefficient, and will take much longer than a properly-sized charger.
Can you have too large a battery charger? No, you can't. Provided, of course, that charging voltages are properly controlled.
Another way of putting this is that LA batteries are self-limiting: they'll take whatever charge they're gonna take, and no more, provided you control the voltage correctly.
Of course AGMs and gelled batteries change the equation somewhat. Gels can take 20-25% of their capacity in charging amperage when at a 50% SOC. AGMs can take over 100% of their capacity when at 50% SOC. And, when discharged to 20% SOC, AGMs can take five times their capacity in initial charge. That's right, a 100A AGM
@ 20% SOC can take 500A initial charge.
And, this may surprise you: this incredible high amperage is actually good for them.
What won't surprise you is that very few boats (none really) have anywhere near enough charging capacity to take advantage of AGMs incredible charge acceptance profiles. For most cruising sailors, switching to AGMs without a thorough review and upgrade of your charging systems is just throwing $$$ away.