I would use as heavy a top as one could afford and be able to manage into a table. At least 3/8" or better, but anything over 1" may be overkill for most purposes. I once worked for a guy that built his table out of 1/4" for the top and every time you banged on it it would bounce and clang most unnecessarily
The thicker the top, the quieter it is when you hit it. Sure its not an anvil, but you WILL be hitting it from time to time
I would make it as big as you can for what room you have and the size of your most common projects. i. e. If you do lots of gates, make it a big as the largest gate you will make a lot. I have a solid core wooden door for my table. Great size, lousy welding table, but the price was right
