Ultima Matrix blades have a 30 day guarantee. I am thinking of taking advantage of it myself :-) Currently I have Ultima Matrix Legacy (I switched from a Coronation Ace,which is the blade that Legacy is modeled after, so the adjustment was minor). I love the feel of that steel on the ice in comparison with the carbon steel Coronation ace!
My coach (who skates on Gold Stars) thinks that the profile of the Legacy makes it very easy to toe scratch- she mentioned that she notices it a lot with her students who switched to Legacy. Another skater at my rink (older adult, former national competitor) says that it was difficult for her to skate in MK Professionals (which are very similar to CoroAces and Legacy), she did a face plant on a spiral, because the ride to the toe pick was so short. So she switched to Gold Star (which is similar to Gold Seal and similar to Ultima Matrix Supreme) and loves it.
So, long story short, my coach suggested that I look at a a Gold Star or Gold Seal, and I am considering trying Ultima Matrix Supreme (which is a Gold Seal analog), since the steel is so nice :-) If they don't work for me in 30 days, then I 'll stay with Legacy.
All that being said, blades are a highly personal matter, unless you have tried different ones, there is no way to know (and even then it varies from one person to the next!). Lots of kids at my rink happily skate on Legacy, so I don't think you will be disappointed. On the other hand, you want to minimize adjustments to blades, so if you are able to try out a higher level blade- I would say go for it. It is expensive, but if your feet stopped growing, makes sense.
Boots are a whole other matter. I think no matter how much research you do, until you have skated in them for a couple of months, you really don't know how they will work out for you. I have Riedell 875, which were a comfortable boot to break in ( I am an adult with all my single jumps, working on axel). I did have some issues with the landing foot, but a thinner tongue solved it. After having skated in them for a couple of months, I noticed that they stretched out a bit and now don't feel as great (too long and wobbly heel). So, I decided to bite the bullet and go with custom Harlicks (my feet are different sizes, so stock boots end up being too big for one foot). I just placed the order, so I don't know how they will turn out.
Riedell has exceptional customer service, you can't really go wrong with them (if your foot matches their last). From my understanding, Riedells are better for people with a less pronounced difference between the ball and the heel. I would also recommend looking at Riedell 435 for you, which are like 875 but not as stiff.
I see a lot of Jacksons as well at the rink on people ranging from beginner all the way to advanced level. I tried on a Jackson Premiere- felt very stiff and not as cushiony as Riedell.
Good luck with your decisions!!! I know it is overwhelming with all the choices out there.