The 150's O-200A produces (supposedly) 100 hp. Its dry weight is 190 pounds.
The 152's O-235-L2C/N2C produces 115 HP. Its dry weight is 249 pounds.
Yup. It's heavier.
But the O-200's power-to-weight ratio is 1.9 pounds per HP.
The O-235's ratio is 2.16 pounds per HP.
So the Lyc is about 11.4 % heavier that way. It's not as if it was 25% heavier or something.
Here are the tradeoffs for that extra weight:
The O-200's TBO is 1800 hours, and you can expect valve work by half of that time.
The O-235's TBO is 2400 hours, and the valves will go the full TBO.
The O-235 runs cooler than the O-200.
The O-200 generates its max HP at slightly less RPM: 2700 as opposed to 2750. That means slightly increased propeller efficiency due to less drag.
The Lyc runs smoother. It doesn't ice up its carb nearly so quickly as the O-200. Its starter makes far less trouble than the 0-200's and costs less, once the cost of the Bendix clutch/gear assembly is figured into it, and that part is the chief source of trouble. Cheaper to replace the starter with a B&C or Skytec and eliminate that clutch.
And then there's the widely suspected (more than just suspicion, in my experience) that the O-200 doesn't really produce 100 HP. Some people with engine dynamometers have seen it.
But the "gullwing" prop on the 152 has an AD against it that demands NDT on it every 750 hours. I believe there is an STC to replace it with a safer prop.
https://drs.faa.gov/browse/excelExternalWindow/10D7120761741D79862576D30052CA66.0001