So there's three things here - driving line, setup, and how the cars are designed. Let's address them one by one.

1.) Driving line and setup: 17.5 requires you to take a different line than mod for jumps, especially for big jumps that you want to clear. I will grant you that, but as somebody who races both 17.5 AND mod, I will tell you that I personally enjoy having to view the track differently between mod and 17.5. What do I care about having to double-single in 17.5 when I'm also racing a mod class where I triple? It just adds more variety to what is otherwise the same layout. The gearing part is something I find interesting, because in 17.5 you are generally trying to run the motor as hot as you possibly can to keep the car quick. In mod, you have the luxury of high kV which allows you to gear down and still go fast. So I do take some enjoyment out of really trying to squeeze as much as I can out of the motor through gearing and timing, especially for different layouts and surfaces where you'll have to make some adjustments to deal with the speed/torque trade-off. You just don't have to do that in mod, since there's already so much motor. Maybe I'm just being nostalgic, but this is the kind of tuning you had to do in the brushed motor days where the output power was in the 200-250W range. By comparison, a Sonic 17.5 is 192W while a Sonic 7.5 is a ballistic 427W.

I will not go so far as to call one more technical than the other, but I suggest you not understate the effort it takes to really go fast in 17.5. They're just different. It's like in full scale racing when people talk about how much fun they have with a Mazda Miata or a Mini Cooper. Sure, a Ferrari 458 Italia is faster, but it is not necessarily more fun. It's just different. And if people want to call me a cheater for being faster then they are, then have at it, because it will not take away from the intellectual satisfaction I get from drving that class.

2.) How they're designed: In what way are you referring to design? Do you mean the suspension geometry? The B4 has largely the same geometry as the original RC10, with the only difference being a narrower chassis and wider arms for less camber gain and tire scrub. That has more to do with the change in track surfaces over time than with the increase in motor power (surfaces are less loamy now than back in the day, which means less chassis roll and camber gain are needed to maintain grip). Or are you instead referring to the materials used? The original RC10 had an aluminum tub with some nylon and fiberglass parts, then added a few graphite parts, then eventually went to all carbon composites. That was not motivated by increases in motor power. It was simply the by-product of advancements in materials processing which gave designers another way of going faster with lighter components, regardless of the motor. So, modern r/c cars aren't designed with a particular motor power in mind. They're designed to jump, land, corner, and be as light as possible.

Anyway...17.5 is fun. Mod is fun too. I like both.