Id heard both.
Didnt think much of it until I brought in two white hooved horses and both had to get shod. Id rather stay with dark hooves now.
(exception to my little grey arab filly)
I don't mean to sound disrespectful, but anecdotal evidence on only 2 horses says nothing, especially when we don't know what their prior or current development, management, diet, trimming, etc is like. There have been some good studies done into pigmented v's unpigmented feet, which show there is no difference in strength. If they were indeed weak, you wouldn't see any white footed wild ones, and appys & such with striped hooves would likely have incurable splits galore. ...And far from being 'needed', we'd probably find shoeing of white hooves was contraindicated because the feet were too weak to hold them for long.
Regarding what you should do with your newbies, I strongly advise learning the theory behind 'natural hoofcare' so you can make your own informed decisions. hoofrehab.com is one great place to start, as is barefoothorse.com There are of course good farriers around, but if you're not sure just how good/knowledgeable yours is, I'd personally prefer to go with a good 'hoof care practitioner' as then you know they have a good understanding of the mechanics and other factors affecting hoof function & health. If your mare hasn't needed hoofcare because of her environment & lifestyle, great! You're(& she is) very lucky.(I wish - do my guys every few weeks here!) You'll probably find the new ones only need one or few trims to get them on their way. But depending on the state of the new mare's feet, esp heels/digital cushions, you might find she could benefit from a little longer heel &/or boots when ridden, in the short term, to help her comfortably land heel first & therefore build up the strength while still getting a bit extra protection. Your weanling is likely still light enough to cope without, and will have grown strong, well developed feet by the time she's mature on this sort of environment.
Sending us some hoof pics, of all your horses, of various angles will enable us to give you an idea of the specifics that may be needed for their feet. Telling us about their management, amount of exercise, diet, etc might also lead us to suggestions that you can tweak to help them even more.