I suggest to use a tablet for a month or so. It's cheaper than a good mouse, pen is lighter and absolute positioning doesn't have a mouse drift issue. Also you have a one of the best models for osu so def try it. Some people find tablet just better for osu and most of the top players use tablets.
Anyway final decision is up to you because it's a matter of preference. Personally, I am on the tablet side of the community, but your opinion might be different.
PS. Do not forget to install OpenTabletDriver drivers for tablet. Wacom drivers have a bit of latency and aren't as flexible.