Sorry if this is stated somewhere else but I cant find a definitive answer
The recommended driver is always the latest one provided in the download tab of the product page. However, it depends on the other products (specifically advanced wheels) being used as well. So in the case of the V2.5 base, because it has been on the market for some time, the download page currently has 311 and 328, which are relatively 'old' drivers, but they are solid. If you are using one of the older generation steering wheels that doesn't require its own firmware, like a BMW GT2, CSL Elite P1, Formula Carbon/Esports, Universal Hub, etc, then 328 will be perfectly fine.
If you are using one of the newer generation wheels that requires its own firmware, like the Formula V2, Podium Hub, then 328 is too old, and the V2.5 will need to be updated to support such a wheel. Therefore you should download the driver package from the download page of the steering wheel instead, because that will be newer. Each driver package always contains firmware for every product, so the driver you download from the steering wheel page will contain firmware for the V2.5 base as well.
Alternatively, you can download one of the beta drivers from the forum in the Beta Drivers section. But these are named beta drivers for a reason. They are safe to try, and can offer improved performance and compatibility, but they are not necessarily as stable as the drivers found on the main website. 346 is considered to be the most stable of recent beta drivers.
Naturally we would like to improve this situation. Ideally we would just have a single driver package that contained all the latest firmware for every single product, and everything would just work. But we have a large and growing ecosystem, and it is a very complex task. There are big improvements coming.
[Fanatec Community Manager]
Can you tell me how loud the fan is supposed to get too? after about 10 minutes it sounds like a hairdryer & its causing the chassis to vibrate at the back. If I hold my finger on the fan grill it stops vibrating but its loud. ive tried 2 different driver packages 347 & 365.
edit_ So basically because I use a Formula Carbon wheel there I may as well use v328?
If the fan is so loud, go RMA.
(and then use driver 365,it improves force feedback with csw2.5)
As Aurelien says, if the fan noise is disrupting your enjoyment of the product, please create a support ticket. The loudness depends on a few factors, but it should rarely have to operate near to its highest RPM. Firmware updates can affect fan profiles, but the way you have described the sound leads me to believe there could be a hardware issue that can't be solved with updates. Providing a video (with clear audio of the fan) will also help the team assess the problem.
Thank You. I'm going record some noise & make a support ticket.