i battle across divisions quite a bit. i am not 100% sure but i am pretty confident that when you say "Or am I wrong to assume that there's an inherent preference programmed in for kids to favor higher-division offers than they would lower ones?" that you are making a bad assumption. there is something programmed that makes the kid willing to talk to you or not based on division. but once you are talking about a guy both schools can recruit, there is no built in advantage. i assume you mean other than the obvious ones that we can see, like money and prestige.
for simplicity, its safe to say the higher division school will always have a prestige advantage. if you look at an a+ d3 school and a d- d2 school, i would say the difference is the same as half the difference between an a d3 school and an a+ d3 school plus half the difference between a d- d2 school and a d d2 school. so, in d2 to d3 battles, this might be the same as saying its a partial grade of prestige in d2 or d3. but in d1/d2 battles, its probably less than a partial grade of d1 for an a+ d2 to d- d1 school. so if its an a+ d2 school vs a c- d1 like in your original question, i would say it is slightly more than a c- to d- d1 school. if you think prestige difference are added (like the difference from A to B is twice the difference of A to C), then i would say its the sum of the d- to c- difference plus the d- to a+ d2 difference. if you think prestige difference are multiplied (like the difference from A to C is the square of the distance from A to B), then i would say it is the product of the two factors. but in any case, for an a+ school down a division, the difference is basically the same as the distance from the higher division school to the worst prestige school in the division (so for an average c-, the worst is a bad d-, which is 3.5 partial grades).
the money is also a built in advantage for higher division schools. that 3 to 5k difference in d3 to d2 is not that serious, but 15k to 5k for d1 to d2 is. however, distance directly counteracts money. so often, if you look at the money/distance situation, the lower division school is in much better shape. also, higher division school generally have to spend more money getting the other players i get. so its really very feasible to win battles a division up. you just have to pick you battles carefully. i don't have as many teams as most people, but i would guess that i probably battle up a division for a higher % of my players than any successful coach out there. from a high level, i would say i win a large majority of these battles, but i also turn down a ton of potential battles because i won't win them. if you look at all the possible battles up a division (for players you would like to have), you will lose most of them. so the key to battling up a division is knowing when to take the chance and when you would just be throwing money away. also, how much you could get for your money elsewhere has to be a major factor in your decision.
so all in all, i would say battling up a division, especially vs sims, is very feasible and can be quite valuable. but not nearly as valuable as the amount of damage you can do messing it up. i think its fun, and i put learning before success - so i often went looking for battles up a division, and i took quite a few beating early in my career losing those battles. in retrospect, it was well worth it. so if you have a team you don't love to death, then i would probably recommend taking the battles when they seem feasible, but going looking for them, that is probably not very smart ;) you just have to be prepared to lose. expect to lose, at least for a while.
how far can you go battling up a division? against sims, really quite far. if a recruit is not a prime target, pretty much any d3 school can poach off any d2 sim (assuming they can talk to the player in the first place). in d2, you can poach off pretty much all the sims. humans are always a bigger risk - because you often have to have reason to believe they spent a good chunk of cash elsewhere to think you can win the battle. and other times (hopefully not the same times, but sometimes it is), you have to bank on the higher division coach not being willing to spend his money on this guy, because he has other options, even though he could certainly beat you if he tried. i usually stay away from those but not always. i have beaten an a- d2 human coached school from an a+ d3, and he really wanted the guy - but i had distance. the other guy was a good coach but i found out he did not spend his money optimally so i might have lucked out a bit too. i've also poached many a player from D range d1 schools, i think i have beaten a c- human but am not positive. i almost won a player off an a- prestige school in one of the top 2 bcs confs in tark, but sadly, it wasn't meant to be. i could have won if i went all out, but i had 5 or 6 scholarships. i pretty much knew from the start i would probably win if i went all out and would probably lose if i didn't, but i didn't have much else to do with my last 15k or so, so i went for it. also i was ****** at the guy. other than that one, i may have won as many as my last 10 battles up a division, so you can get it to the point where it is pretty safe.