This is an excellent dictionary for day-to-day use. However if you are travelling to China there is no point buying it before you go. There are countless dictionaries exactly like this on sale in bookshop throughout the PRC for a fraction of the price. Therefore at this stage the size should make no difference: if you want it to travel with you should buy it later anyway; if staying at home then go for the larger 2nd edition which contains better example sentences, a larger range of binomes and more complex vocabulary.