The differences of the Epson 4870 vs. the 3200 are best summarized in three points:
1. The maximum resolution for scanning on the 4870 is 4800 dpi vs. 3200 on the 3200. This is important when scanning smaller format film, which needs the extra resolution for quality enlargements. In fact, one cannot use the 4800 dpi setting on a 4x5 piece of film anyway. The max the scanner will permit for a 4x5 tranny is 3200 dpi (which results in a file size of 1gig! So, if you plan on scanning more medium format film than 4x5, the extra resolution may be worth the higher price. As for 35mm, you are almost surely going to obtain better results with a dedicated 35mm film scanner than you will with a flatbed, so this shouldn’t factor into your decision.
I actually only use my 4870 for scanning 4x5, using a Nikon 8000 for medium format and 35mm.
2. Digital ICE. While this significantly increases the scan time (from 45 minutes to 5 hours for a 4x5 transparency at 3200 dpi on my G4), it saves an inordinate amount of manual labor spotting out dust from continuous tone areas like sky or water. The amount of dust can be reduced by spending more prep time cleaning your film and scanner bed, but some always seems to sneak in. I opt to ease the pain by running 4x5 scans on my Epson overnight with ICE, starting it just as I head off to bed so that a scan is waiting for me in the morning.
3. Price. You know what you want to spend. You can save some money buying the 3200, but you pay for that savings in your time.
Some final thoughts. It is not necessary to purchase the more expensive Pro model 4870, which just includes more software. The Epson scanning software that comes with the basic 4870 is easy to use and results in remarkable scans.
Charles Cramer uses his Epson 4870 to proof his 4x5 negatives. He finds it does a better job for that task than the TANGO drum scanner, and it is a much simpler process than wet mounting the film. He still scans his 4x5 transparencies on the TANGO, but notes the perceptible gap in quality has narrowed considerably in recent years. So, ask yourself these questions: What type of film will you be scanning? What size will your enlargements be? How much is your time worth? And, what can you afford to spend?