carlos danger

The only rear difference between 240 and 350 is that the hubs are slightly heavier and they are made in taiwan, any maybe may use lower grade alu. and also use carbon steel bearings.

the 240 is made in switzerland (supposedly) and is lighter. and has stainless bearings.

i personally would get handbuilt ones. no matter the hub. I'd probably get 350 hubs if money was tight, they cost about as much as ultegra hubs. and the rear is about 100g lighter. but the genersl construction shimano vs dt is very different. the dts are built to never be touched until you have to swap bearings, (could take 15000-20000km or more) and the shimanos are made for an initial service before you even start using them.

i will try to explain how the grades work.
dt240 swiss made, stainless bearings. lightest. (you can get a steel freehub for these, and weight goes up) 250g for a rear and 105 for a front hub.
dt350 taiwan made and non stainless bearings. heavier by maybe 100-150g or so for both. less exotic machining. but tyhe 240ies are not in any way machines exotic, i'm a machinist by trade.

shimano dura ace - ti freehub, the mech is in the freehub, alu oversized axle, polished and exotic coating (some carbide/oxide/nitride) on bearing races. lightest. maybe 300g, like 50 g heavier than dt 240.

ultegra. steel freehub. alu oversized axle, 100g heavier or so than DA because of steel freehub. everything supposedly the same.

105. steel freehub, lesser exotic polishing and machining of races. maybe steel axle that is non oversized. and will therefore have bigger bearing balls in the freehub and all over.

lesser than 105: steel freehub, regular machines races, steel axle not oversized, big loose ball bearings since the axle is smaller, more/bigger balls in the freehub since the axle is smaller. a rear weighs about 400-450g. it will last until the end of eternity if lubed when new and taken apart and adjusted.
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shimano did the same this wuth the MTB hubs. where the slx hub was the all steel ones. and those were the best for durability. xt the worst and xtr the so so ones. you do the math.

I think the dt240ies are worth it since the stainless bearings seems to run forever. at least 15000km in the rear. with nothing done. and its very easy to service the mechanism. takes maybe 2 minutes.

I can do a shimano mech in 2minutes too but i have done them like 100 times. you definitely can't.

If i was going shimano i would go the all steel hubs (steel thin axle, steel freehubs look in the docs to determine, these are the lower grade ones 105 and lower). sure they are heavier than dt240 by about 200g out back and 50g up front heavier. but you can service them with only tools and grease. I have not noticed any difference in speed with 240 and slx hubs, and the slx were on heavier less aero rims too.

ymmv though. I also have dt 350ies. discs. the 350ies are good enough to be honest. minimal difference compared to the 240ies in reality. except the bearings. if i dont have to change the bearings in my hubs for an extra year thoug, i'd say 150-200€ is worth it. for the convenience alone!

Not getting any wiser i guess?? Neither did i, so i simply got all of them.

PRIO 1 for u is getting handbuilt wheels no matter the hubs or rims imo!! you will thank me later. even though dt wheels are good they are never as good "custom builders ones, never will be, not gonna happen.

just wanted to point this out since this is much much more important than your hubs. just saying!!