Not really. Comlex has it's main focus on clinical vignette presentation of patients, you really need to look for trends, constellation of symptoms, buzzwords, you need to be familiar with MOST LIKELY type of questions - that sets off many students who only did UW, just because UW won't ask/teach you that. You have to know 1st most common and often 2nd most common bug/drug etc. A lot more neuro, ob/gun, micro (with bugs that you won't see in UW or FA) and nitty gritty anatomy heavy msk that UW won't test you on. Comlex neuro is often more convoluted. MSK is often full of specific primary care details and so on. And only then, yes, you have on top of this OMM (which is often very lengthy questions), law stuff that you might get about 10-15 questions on comlex and none on USMLE. Add to that some 10-20 questions that you might encounter asking straight level 2 stuff - like next best step/treatment etc. In short it's a must to do comquest and UW. Doing just UW you are just lowering your comlex score. For some it might not matter if you have good step 1 score, but not everyone has a good step 1 score, so.....
P.S. BTW comquest explanations are on same UW level and even better explaining exactly why one answer is most likely as opposed to another answer. I did half of comquest and it teaches you very well to understand what you are asked. It turns out questions are not vague or poorly written like many on sdn like to repeat old mantra, but in fact they are specifically asking you for a knowledge on top of just knowing what drug can treat this disease, they are asking you to know several drugs and chose the one that is most appropriate in this specific situation. You'll need to know a bit of clinical real life situation and a bit of statistics to chose correct most likely or most correct answer. Doing only UW you will be tripping on questions like this and then come to sdn to bitch about it, when in fact you lacked knowledge or understanding to properly answer the question asked. It's kinda like reading comprehension too lol, it's not only pure 1 straight fact to know like in UW. Nope.