Hi, just wanted to chime in with my experience. My DD is 11 now and has been sleeping in an Ikea loft bed (the taller one) since she was 6. I'll give you the positives and negatives from my perspective.
The biggest downside to getting this bed was that I totally freaked out about it once we had it set up. For weeks, I allowed her to play on it, but not sleep in it (she slept partly in my bed and partly on a mattress on the floor beneath her loft bed). Then, I let her sleep in it, but put a mattress on the floor beneath it (where she would fall, if she did) because I was convinced she would fall out. I lost a lot of sleep worrying about this! The other downsides are that: 1) as someone else pointed out, it's a pain in the neck to change the sheets and rotate the mattress, 2) no possibility of a bedside table (we have hanging baskets attached to the side rail where she can keep tissues, her glasses, etc., 3) it can be challenging to keep your child's friends / siblings off the loft during playtime (which could be dangerous), and 3) it's more difficult to read stories and snuggle at night with a loft bed. Although my DD is nearly 12, I still snuggle with her and massage her back every night as she falls asleep. It works out only because I'm pretty small and light myself, but I imagine if I was a regular sized adult, I might not fit up there with her. I do cherish that snuggle time, and would hate to give it up just because of a bed configuration. Just something to think about.
The positives of this bed are that, 1) my DD loves it 2) it creates a lot of extra space in her (smallish) bedroom -- we put an Ikea Billy bookcase beneath it for toy and book storage, then plopped an area rug and two bean bag chairs under there as well. Instant reading / playing / hanging out area! During sleepovers, we put an inflatable air mattress in the space beneath it, and there's room for 1 or 2 friends that way. And of course, 3) she's never fallen out or had any other kind of injury in the nearly 6 years she's been sleeping in this bed. One of my other concerns was that she would get up to use the bathroom in the night and not be able to negotiate the ladder in her sleepy state, and take a tumble that way. But that's never happened either... she can do it in her sleep.
We have a few friends who have gotten the shorter model you're considering for their kids and that's worked out great for them. Good luck with your decision!