@Jitterfactor - of course, you want to do both, if possible 
With a future-looking attitude, it is probably interesting to note that we are experiencing also both developments: image resolutions are going up and HDR is becoming mainstream. So, what’s in the basket for both?
Well, both topics, image resolution and HDR, require more resources and investments, the better you want to get with them - both in real $ or €, in scan and processing time as well as storage requirements and internet transfer times.
Resolution can be discussed endlessly. On one end of the scale are the ones that want to “see” every single grain of the original movie source, on the other hand there are the ones that apply heavy filtering anyway to get rid of all the grain and other image imperfections.
Note that the later, grainless approach gives you alos nice file sizes for streaming the material.
There is probably a personal sweetspot with respect to scan resolution, and it depends a lot on the material in question. A Super-8 film will be very different from a 16 mm film in terms of resolution needed. Also, normal reallife film is different from animation material - the later has more evenly varying image patches and it might not look nice if homogenous color patches feature too much noise. On the other hand, to faithfully capture the shape of the brush strokes, you might be tempted to go for a higher scan resolution and reduce noise in the post. In the end, it’s a balance between personal tastes and the intended audience/distribution plattform.
If you are aiming at archival purposes, the best scan resolution is probably the highest you can afford. You can always reduce resolution and grain during postprocessing. Your archival copy might also be re-rendered at a later time with higher resolution, once higher bandwidth distributions become available.
By the way, HDR is a generic term and needs to be split into different topics. Originally, HDR did refer to an image capture process which records the full radiances of a scene faithfully. You need special image formats for such a thing, like the OpenEXR-format for example.
Now, the images we are used to see in normal life are not radiance images - they are tweaked in a way that there’s a midtone range which features a nice contrast, and while the highlights burn out into pure white and the shadows dip into black. If you look at a radiance image unprocessed, it in contrast looks rather dull.
In order to get a useful image, a secondary process called tone-mapping is necessary for a real HDR image. Basically, in the tone-mapping step, the contrast range of the radiance image is compressed in such a way that an image is obtained which looks “right” in our eyes. Simultaniously, during tone-mapping, the immense range of pixel values of the original HDR (high dynamic range) image is reduced to obtain a LDR (low dynamic range) image which can be stored, transmitted and displayed on usual hardware.
The typical LDR image features 8 bit per color channel - that is also probably the bit-depth your monitor is currenty working with. An HDR-image format, like the above mentioned OpenEXR can sustain practically unlimited bit-depths per pixel.
Somewhat inbetween are captures in RAW-format. Todays camera sensors operate with anything between 10 bit to 14 bit. That is too much for current display technology (remember: only 8 bits per color channel, maybe less, but no more), so people need to “develop” their RAW-files. That step is equivalent with the tone-mapping step mentioned above for HDR images.
“Development of RAW” or “tone-mapping of HDR” imagery is actually a very subjective thing. The reason is that you need to decide which of the immense tone range you have available do you want to use. Will you sqeeze the whole dynamic range into your small LDR-range, resulting in a dull image? Or will you allow a lot of shadow detail to be lost, recovering in turn dynamic range for you mid-tones? Or does it not matter if the highlights burn out, enabling you to keep some important information in the shadow regions?
There’s still another thing which is also called “HDR” and which I probably need to discuss here. Modern mobile cameras feature such a mode, for example. Even some sensor chips have already build-in “HDR” modes. What is this? Well, basically, the camera takes here in short succession two or more exposures with different exposure settings and combines (tone-maps) them into a single LDR (8 bit per color channel) image. While the algorithms that combine these different exposures are usually not disclosed, my best bet is that they are similar to “exposure fusion” which I described already on this forum on several occasions (see here for some basic examples and here for a comparison between HDR and RAW capture).
At this point in time, I am not aware that anybody has used a sensor or camera with build-in HDR capability. So the normal route to obtain a “HDR” (=a LDR derived from a real HDR) is to take several differently exposed LDRs and combine them during post-processing in one way or the other. Clearly, there is not really a cost factor attached to this other than your personal time, safe of the need for extended storage space. You might need some technique to ensure perfect registration of the different exposures of a single frame. Otherwise, you can use the image resolution of any camera you can afford.
From my experience, the most limiting factor with HDR-scanning is the additional time it takes to capture and process the different exposures.
Because of the time factor involved in HDR capture, utilizing a single RAW capture with a high-quality camera might be a better way to proceed. A single RAW file needs much less data to transfer and store. And the technique is already build in cameras, software and post-production workflows.
Note finally that commercially produced material is usually optimized in such a way that the dynamic range stays anyway within certain limits - so a real HDR capture might not be needed at all. That is even more true for animations which are already recorded in a very controlled way in the animation studio.