I've cleaned hundreds of walleye both ways and the electric makes a nicer fillet in my opinion and wastes less meat
Again in my opinion
Now if you clean fish similar to Simon's "unders" all the time then a manual blade might suit you... Unfortunately or fortunately depending how you look at it my eaters are typically 22-23" class fish
I don't clean my fish like I'm in the Indy 500 but I get em done quick enough for me... And I know my fillets look nicer then I ever got em with a manual blade
If you can do em faster and better with a regular blade all the power to you... It's just personal preference... I can do em both ways but prefer the manual
Now perch cleaning is an entire other thread lol