Maybe, maybe not. How often do you use the 10-bit mode on your present SDS2000X+? And when you compare it to the 8-bit mode, do you think "gee that's a lot better but I'd be willing to pay a lot more for further improvement"? If so, 12-bit is definitely for you. If you don't use the 10-bit mode or can't tell the difference clearly enough to matter, then 12-bit won't change your life. For me, given the limited resolution of the screen itself (which is the same on both scopes) the place where more bits matters enough for me to care is when I'm using the vertical zoom feature to look at something. Do you use vertical zoom?
12-bit oscilloscope offers higher resolution, a wider dynamic range, better signal fidelity, and a lower noise floor compared to an 8-bit oscilloscope. These advantages make it suitable for applications requiring precise measurements and analysis of signals, especially when dealing with small signal amplitudes or capturing fine details in waveforms. However, I agree with you that for many general-purpose applications, an 8-bit oscilloscope may suffice and be more cost-effective.
Perhaps on one instrument, but if you apply that same thinking to the rest of your bench and end up with a few more digits on your DMM, better specs on your AWG, etc etc you might end up with a substantial "investment".
I don't want to focus solely on the financial aspect, but I believe it's important to mention that the device in question would cost me around $1K.
To elaborate, I have already sold my Siglent SDS1104X-E for $500 and finalized a $200 deal with a buyer for my Tektronix 2430A, which has only one working channel. Additionally, I intend to sell my SDS2104X Plus for minimum $1,250. Altogether, create total budget of around $2K from these three devices. With the potential tax advantages, I would only need to pay around $1,000...
Perhaps the question becomes clearer: "Is it worth investing $1,000 for the new features?"