Looking on the internet deeply has found these results:

with this matter is the most popular phrase on the web.

in this matter 141,000,000 results on the web	with this matter 145,100,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
I'm representing ADM in this matter. The Council should take decisions in this matter after consultation of the European Parliament. You seem to be representing everyone in this matter. Whatever options the President is or isn't considering in this matter are private. Your opinion in this matter is very important, sir. I will respect the Avatar's wishes in this matter. I really have no choice in this matter. I need you to be very clear in this matter.	I know that the Commissioner is very familiar with this matter. I should like to ask the Commissioner where we are with this matter. I therefore think that everyone involved with this matter should sign a code of conduct. We'll try not to bother you with this matter again. We've done all we could do with this matter for now. Mr President, I join in the congratulations to all involved with this matter. I want to officially thank all of you for your invaluable help with this matter. Colleagues will recall that we dealt with this matter in urgent procedure in October.

in this matter

141,000,000 results on the web

with this matter

145,100,000 results on the web

More popular!

I'm representing ADM in this matter.
The Council should take decisions in this matter after consultation of the European Parliament.
You seem to be representing everyone in this matter.
Whatever options the President is or isn't considering in this matter are private.
Your opinion in this matter is very important, sir.
I will respect the Avatar's wishes in this matter.
I really have no choice in this matter.
I need you to be very clear in this matter.

I know that the Commissioner is very familiar with this matter.
I should like to ask the Commissioner where we are with this matter.
I therefore think that everyone involved with this matter should sign a code of conduct.
We'll try not to bother you with this matter again.
We've done all we could do with this matter for now.
Mr President, I join in the congratulations to all involved with this matter.
I want to officially thank all of you for your invaluable help with this matter.
Colleagues will recall that we dealt with this matter in urgent procedure in October.