What a provocative and enticing topic. So many opinions and experiences. Here's my two cents, YMMV:
Just a comment about inexpensive boots. I have been on a quest for new boots since my Jackson Freestyles are not only a year old, they are a whole size, or so, too big. I think all of the rental skates fall in the category of Riedell 110's or Jackson Glaciers. That puts them below Jackson Mystiques and Riedell 115s with very little support, especially if you are a big adult. rentals are known for giving skaters a distinctive look: ankles falling in. I also don't think you can change the blades on most rentals because rivets are considered maintenance free and screws need tightening ( and blades could be stolen/changed.)
I feel that they just won't hold up to being "pushed" by more than leisurely stroking around. If you were to feel my Freestyles, you would think they are stiff as a board. But when I start shoving my 6' 2" 195 pounds around and up and down (most single jumps,) they start showing their age. Earlier this year they started falling over on a landing unless I landed on a perfect edge/angle combination. Last Saturday I tried to show off to my new FS group instructor with a very high, sailing Waltz Jump and they twisted on the take off - I really pushed up and off that minuscule toe pick harder than I ever had before. I was impressed that I fixed myself in the air and landed and held a deep edge. The instructor, though, had a comment about my right arm in the air...
So, I am stuck buying a boot of comparable or better quality. I am thinking of getting a pair of vintage glove leather skates on ebay to build my ankles back up. When I first skated in college, that is what an older (70's) gentleman gave me because he felt sorry for my using rentals. I wish I could jump now like I could back then. I also used low cut leather ski boots a shop found in their attic for me (I'm a Minnesotan Gopher.)
The OP commented on the many closure positions with buckles, but they are far fewer than the eyelet combinations. Laces allow the boots to close around the foot at many places and flex/shift to allow the volume of the foot to stay the same, but the shape to shift. Buckles are just fixed and do not allow any change after being snapped.
For inexpensive boots, you could try the Jackson Soft-tecs or Riedell versions. The upper models have good support and velcro.
Riedell Soft Skates
Today I put on my $40 Ultima Freestyle blades that I just got on myskatingmall from Ryan Jahnke. My skates and I had a short one hour session today to try them out. What a difference $400 blades make - I love them. Didn't trip over that nice big drag pick, but the three of us are going to have to work something out for clean three turns and spins. Now, if you can find cheap boots for my "new" blades that will handle 195 lbs revolving at 90 rpm and dropping a foot or so onto the ice at about 15 mph, let me know. I missed out on brand new Riedell Bronze Stars (
http://www.usaskates.com/specials/special23.html) for $49. If you find a deal on men's 10 1/2 or 11's let me know, I spend at least and hour every evening looking...