Some questions/thoughts...
Budget?
Costs of film scanners usually start around a few hundreds, and then go well into the thousands.
Required Output?
Do you need enough scan resolution so that you can make 16"x24" prints from a 35mm negative? This will be one of the biggest factors that will affect the cost of the scanner.
Scan volume?
Are you scanning an entire 36 frame roll every few days? Or the odd select frame?
Format?
Are you scanning only 35mm? Or 120? 4x5?
Software?
Some older dedicated scanners have issues with OEM software and drivers and may be limited to using somewhat expensive 3rd party software.
Given the above questions, I personally think that the best overall value in scanners available are the Epson V7xx/V8xx models.
Flatbed scanners don't have quite as high scan resolution as dedicated scanners, but I can get good enough 35mm scans from my V750 for 12"x18". Prints that I have shown in galleries.
I have found that the Epson software is actually very good and allows the most user control of output.
I wrote a detailed guide to using Epson Scan her,
Getting the most from color negative film with your Epson flatbed. – Photography by Colton Allen