The Olds 307 was and is a very good engine. Actually it is derived from the low deck 330 that first appeared in 1964. This was an all new design and very up to date for the time. The high deck 425 followed for 1965 in which the 455 was derived.
The 307 was the only long stroke engine of this family, thus it had good low end torque, fuel economy and emissions qualities. That is perhaps the reason it was used over the Chevrolet 305 during the '80's. This generation of Olds engine was known for it's durability, good performance and relatively good fuel economy. It is a much better quality engine than the Chevrolet engines, actually as close to or the equal to the famed 472.
However, the 307 is a bit tricky to keep properly in tune, and the 3C system is somewhat complicated using an electronic feedback carb and miles of vacuum hoses and multiple sensors. After much work, I have finally got the 307 in my '89 Brougham from a gas sucking powerless pig to one that runs nice and responsive, decent power and excellent fuel economy. But, it is still no powerhouse. Around town power is excellent, but highway power is a bit off. But still it is the best running 307 I have yet driven. It will cruise easily at 70 MPH loaded with the AC on.
The 4.5 in my '88 Eldorado is also a sweetheart. It just runs very good. I have not had to really do anything to it. It goes like stink, is very responsive and delivers phenomenal fuel economy.
The Chevrolet engines are also very good. The L03 and L05's are incredibly durable and simple engines. The TBI is a very simple and durable design. Of coarse we all know that these engines go back the the original SBC of 1955.
The LT1 is also a very excellent engine. Power is 260 HP compared to the 170 of the L05, which is a huge leap. The engines will also rev quite freely. But torque output at lower RPM's is not a lot greater. They are of the highest development of the SBC utilising reverse flow cooling to support a lofty 10.3:1 compression ratio. But the achilles heel of this engine is the Opti-Spark. It can be problematic and expensive to repair. Again, many give little difficulty over their life, particularly the 1996-95 units that were vented.