They are almost the same in both grammar and pronunciation, only very few differences exist. However, the expression habits of a same thing can sometimes be the major difference.
For example, the word 'internet' is 互联网(互聯網 if in TChinese) in SChinese and 網際網路(网际网路 if in SChinese) in TChinese.
the word 'panda' is 熊猫(熊貓 if in TChinese) in SChinese and 貓熊(猫熊 if in SChinese) in TChinese. It's very interesting because they are just inverted!
and the word 'taxi' is 出租车(出租車 if in TChinese) in SChinese and 計程車(计程车 if in SChinese) in TChinese.
※SChinese stands for Simplified Chinese and TChinese for Traditional Chinese
And there are so many such examples. However, if you use a specific S/TChinese noun to a T/SChinese speaker, he can still understand what you mean, only sounds a little weird.