I have owned both the lionel and the Sunset 3rd rail Dreyfuss. Both of them are great runners. I ended up keeping the Sunset 3rd rail version because it matches the Golden Gate Depot 20th century cars. Also, the detail on the Sunset 3rd Rail is incredible. Each time I purchase something from Sunset 3rd rail, I am more and more impressed with the models they make. That being said, they are very hard to find on the secondary market and the Sunset 3rd Rail engines are much more fragile than the lionel engines. I would strongly recommend only buying one in like new condition if at all possible. However, If you do purchase one that needs work, they are very helpful in repairing it. Also, I found that my Sunset 3rd Rail hudson required a little more time to be properly broken in than than the lionel engine whiched seemed to run great right out of the box. That being said, now that it is broken in, it runs great. You also were wondering about sound. The Sunset 3rd Rail hudson has the option to chose 2 or 4 chuffs per revolution where the lionel hudson is always 2 chuffs per revolution, making the sunset 3rd rail sound more prototypical. Also the Sunset 3rd rail hudson has a fan driven smoke unit where the lionel hudson has the older style suction smoke unit (not sure what it is actually called) but the sunset 3rd rail engine smokes better imo. Here is a link to a video of my sunset 3rd rail hudson...
http://youtu.be/I6vhVHvmWXY ...
In summary, if you can find a sunset 3rd rail hudson then be ready to shell out some cash and get it while you can because they rarely come up for sale. It took me about a year and a half to find one.
On the other hand, the lionel hudson is a solid engine which runs great and will pull anything you want it to. Also, I have a lionel Dreyfuss for sale right now if you don't wish to search for the sunset 3rd rail Dreyfuss or want something to enjoy until you find the sunset 3rd rail hudson (which is what I did). I am only selling it because I finally found the sunset 3rd rail hudson. Lmk if you are interested, I would like to sell this engine and I hope my review was helpful.