I owned a 352 before I traded for the 402, and I can say the 402 sounds better. So my theory is that McIntosh would make improvements as they introduced new products. I had looked at the 300 before buying the 352 but never really listened to it. I am quite sure that they introduced the dual balanced circuitry with the 352 which made for a quieter noise floor. You may do some research or call the folks at audioclassics.com, they are very knowledgeable about Mc gear and have a passion for the brand and live to help. They also offer a LED light kit for the 352 if you decide when the bulbs burn out that you don't want to deal with changing them again.
I guess my vote is for the 352!
I guess my vote is for the 352!