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I only recommend that with which I have firsthand familiarity, or very close secondhand experience, as in a trusted peer's playing of said horn in my presence. Especially no online advice - not even from here - and no sway from manufacturer's reps unless I actually have opportunity to play for more than a couple of toots. Example is a model (newly popular brand) that a retired but accomplished pro in my main (college) group recently acquired that I strongly feel is thin in low registers. My bias is towards long-established brands, and possibly a now-displaced attitude of getting what you pay for.

It's a lot easier in the oboe world. You can count quality makers on one hand, and one company in particular makes some damn good oboes at student-affordable prices, where for all intents the cheapest model plays and sounds (at least in my hands) almost as good as the top-of-the-line. (Centering improves with price, however.)

For new students I recommend against well-used horns, especially oboes. My experience is many have defects that make them too difficult to play well. I had one oboe student several years ago whose parents followed the (oboe-ignorant) band director's advice, and spent nearly a K-buck fixing a "cheap" wooden oboe from a lesser maker that turned out to be a Franken-oboe of mixed parts. The student had migrated from several years on clarinet and had reasonable chops, but we struggled for months getting even tone and intonation, heaven help us on high register. I loaned her my backup (student model) oboe for a concert, and, long story short, she quit shortly thereafter in the realization that her cobbled oboe was unplayably stuffy, which I had previously confirmed but more or less kept my mouth shut. Hence my resistance to used horns of unknown provenance.

I have a new oboe student starting next week. As has become my usual practice since the Franken-oboe experience, first thing I do is check their instrument. I haven't seen it yet, but I think in this case it's a school horn that has had very little play time. If I can't get anything good out of it, they never will, so my plan if that turns out to be the case is to loan my backup and send the school's horn to a trusted shop for rework.

As for used instruments, I always requested that parents bring them to me for inspection, recommend repairs, check condition, check availability of parts, etc. Over and over, I heard parents say, "We'll start him on this old horn, then if he's good at it, we'll get him a better one". My response was always, "so you'll enter him in the Daytona 500 in an old car running on only 3 cylinders, and if he wins the race, you'll buy him a fast car". It always seemed to get the point across. I had no problem with Aunt Sally's old flute if it was in good shape with minimal repair needs, but if the keys were frozen or posts were out of alignment, etc., then a new or at least newer one was required. The same with what we called ISO's - Instrument Shaped Objects - that no American repairman would touch and couldn't get parts for. Yes, we occasionally had the pretty pink clarinets show up and had to have that conversation with the parents.

The "old really-great designs" are wonderful, if you can still find parts. Again, it comes down to serviceability.

With the less expensive tubas, many of them are fine for school use IF the student will take care of them, but kids are hard on tubas, and softer, thinner brass won't help that. When I bought mine recently, I first bid on a good brand horn on ebay that had obviously been a school horn (and was pretty old), because it was beat up in all the right places. The seller said it played well and with a $500 starting bid, I figured it was worth doing (and repairing) if I could get it for $1k or less. It wound up going for $1500 and the brand new Chinese horn I bought was $1800 (I preferred a CC anyway), but I take good care of it.

My middle school band needed a new French horn in a hurry one time, and my go-to vendor didn't have the brand and model that I liked to use in stock, so he convinced me that I wanted the one he did have in stock. It was a bad mistake; I never could get that horn in tune with the others, and he soon was no longer my vendor.

I started teaching 45 years ago, so the "recommended" brands and models changed over the years, of course. Sometimes when those models became prohibitively expensive, I did my homework and found a new model (still an established brand) and had good luck with it, only to see the manufacturer stop making it 2-3 years later, leaving us with clarinets we "hoped" we could still get parts for. On another note (pardon the pun), when beginner-level alto saxes went up $200 in one year to $600 (that was a lot of money in 1977), I scolded my vendor and told him he was pricing parents out of that market and the school would have to start providing all saxophones. 30 years later, I saw parents standing in long lines to buy beginner altos for $2,000. So what do I know, anyway?

Shame on you Bloke, I was expecting a tuba version of:

https://en.m.wikipedia.org/wiki/A_Modest_Proposal