Oh man, you said the 'O' word
Any modern 2-stroke motorcycle oil is going to be better than the stuff available in the 70s. Don't worry about the brand so much, as long as it has the right specification - API TC, JASO FC and / or ISO-L-EGD are what you should look for.
In my 380, I used Silkolene Comp 2 Injector semi-synth for over a decade, bought from the local bike shop. Then I switched to Silkolene's Scoot Sport 2 semi-synth (supposedly for scooters, but it's the same specs as Comp 2) because it was £2 / $3 cheaper per litre.
For the past year, I've been running Mobil-1 2T racing oil, a fully-synthetic high-spec lube, but only because I got a box of 10x litre bottles from eBay for £30.
There's no noticeable performance difference between these oils - all oils that meet the specs above will burn cleaner and lube better than the oil these bikes were designed for.
I don't know how oil prices are in the US, but in the UK, a good semi-synthetic lube of high spec is only 15 - 20% more expensive than a basic mineral oil. Personally, I think those extra few pennies are well worthwhile for a higher-spec oil.
However, full-synthetic lubes can get VERY expensive ... nearly double the price of basic mineral oil and the specs are usually the same as lower-priced semi-synths. So I'd say that's diminishing returns.