From what I heard, Dimension is done or almost done and now a sub of WTS.
If you are talking asking about the international Dimension / WTS, I have no knowledge or opinion.
If you are asking about the US WTS BD, they are a registered CBSX broker dealer (which is good) with a ton of sub-groups (strange model IMO), including Dimension now as well supposedly.
If I were considering working with them, I would first want to know whose money is capitalizing the US WTS BD? Is it trader's money (class B members usually), or is it the Class A (firm owner's money). The CBOE and SEC don't currently ask about this, but the owner's money is the cushion to protect you from another trader or subgroup blowing up, or from the firm spending your capital (which is a capital contribution to the firm, not a customer deposit).
You can read other posts with questions I have, including why they operate with so many subgroups, and if you are looking for training from WTS I would not bother. From what I know, and this may be wrong, so you should ask yourself, you will learn nothing if they tell you that you will learn to rebate trade low priced stocks with their special routes (don't let them call that scalping, it is not scalping, so make sure you get that clarified). Rebate trading is a skill that will not make you enough money to live off in any city in the US, nor help get you a job at any other trading firm since you can not build rebate trading. It is a total 100% waste to learn that gimmick that doesn't work well to begin with.
Read my other posts if you want more opinions. Their balance sheet is also online at sec.gov is another good place to check.
There are a lot of people on this site that disagree with me, so read their posts too. I have yet to see anyone answer about the Class A versus Class B money, so that is the main open question.