I still use my trusty Epson Perfection 3200 Photo Scanner.
Although over ten years old now it is still to be bettered in my opinion.
Some new scanners have slightly better resolution but considering the 3200 photo's 3,200 x 6,400 dpi versus that of 6,400 x 9,600 dpi I don't know who in their right mind would scan at that scale.
Optical Density (DMAX) is still the same for newer models at 3.4 and this is the important area of shadow detail being captured. (Which multi purpose all in one units simply cannot match.)
Consider that the slides I recently worked with were 32mm x 23mm scanned at 2400 dpi.
This translates to a 18.6 mb photo but at 32mm x 23mm.
An average digital camera say 16mb will give a photo of 300dpi at 414mm x 276mm.
This therefore allows the slides to be converted to 300 dpi photos giving 254mm x 184mm. (10"x7").
Had I scanned at the full 3200 x 6400 dpi then these could have been twice the size again.
Remember the original slide is very small, scanning a full 10" x 8" photo at these resolutions makes for insane file sizes and photos become in sizes of feet not inches.
The Optical Density though is the most important function of a scanner when working with slides or negatives either colour or black and white. Colour and tone can be somewhat rescued via Photoshop but if the detail is not there to begin with then you can't hope to produce a decent end result.