I am still using pantech, no problems.
I use the gallon of paint story with customers.
300w is a gallon of paint, I can sell you a quart but the price only drops 5%.
My problem with under 300w transformers is that it is untested (for me anyway). I have 1000s of 300watt cores out there, they all keep humming along.
Also when it comes to size, I think they are small enough as I am the one that has to fit my hands inside to make adjustments and measurements.
Also after re-reading this post, I realized a flaw in the testing of transformers. They all cut the power (in our case) by 10% so if you have 110v at the outlet your 12v tap will only read 11v. Conversely if you have 130v at the outlet you will have 13v at the 12v tap. So to be fair if you were comparing transformers it would only be fair to make sure the incoming current was the same.
I learned this the hard way at a customer's house that only had 105v at his outlet. By law the power company is supposed to supply within 10% of 120v.