hello,
I am finalizing between UIUC iMSM or Aston MiM. both programs are good, however, one has a dissertation, while the other not.

any thoughts?

The iMSM will be more selective and UIUC is a much more prestigious brand with a larger alumni network in most countries. If you want to take an PhD, a programme with a dissertation will be useful. 

Hello,
thank you, can you elaborate on what do you mean by more selective? ie, selective in what? entering? although i have entered with only recommendation letters, CV, and interviews. 
iMSM doesnt have a dissertation, does that mean i cannot purse a PHD after?

By selective, I mean the percentage of qualified applicants who are admitted. 

You can take a PhD without a masters dissertation. 

If your goal is a PhD, why not pursue something that's a bit more research-focused? Having some kind of research output would be pretty important if you anticipate applying for further studies. 

By selective, I mean the percentage of qualified applicants who are admitted. 

You can take a PhD without a masters dissertation. 

There are universities outside the Russell Group. Unlike the UK, where the PhD is often completed in 3 or 4 years, is most countries PhD students have no prior masters.