Suzhou has a better silk market. They get a lot more tourists and much of what they offer in terms of price, quality and selection is better than what you will find in Wuxi. So if you looking to buy your standard tourist type silk products it is worth it to take a trip to Suzhou.

Wuxi has one advantage over Suzhou. If your looking to get some clothes custom tailored for you there are a lot of little tailor shops located right downtown on Hou Xi Xi street. The quality of workmanship can vary but the prices are usually not that bad. (See the Google map for the general location)

Hou Xi Xi sees a few Expats getting their clothes made here, but it is not as yet a tourist market. The majority of people getting clothes made there are still locals.

The last time I had a suite made in Hou Xi Xi, that I could wear in public, it cost me about 700 RMB. This was a few years ago.

More recently, I had a suite made in one of the stalls for just 250 RMB. I know what this means in Chinese and the quality was so bad my wife forbid me to wear this suite in public. 

My advice is bring a sample of what you want made. For example I had a old dress shirt that I loved because it fit like a glove. I purchased the material at one shop and then had a tailor at another shop make up one sample for me. I liked it and then order a few more.

You will have to bargain to get a good price. It also helps if you know something about making clothes since you have to buy the material and they will probably try to sell you too much.