I use QuickPic as my gallery app & overall it is excellent for me. BUT, the image resizing is probably as bad or worse than all of them for output quality. I emailed the developer & while he replied, he basically blew off & ignored my comment.
For better quality reductions I use Photo Enhance Pro but it's not free, as it does do sharpening & mid tone contrast, BUT, neither the amount of sharpening or mid tone contrast are user controlled other than in the overall app settings, so that makes it cumbersome for quick work. After that, one has only 2 choices for output, quick for Web, & High Res. The devleoper says he's too busy to do much more tweaking of the app. It also has other quirks that could be fixed.
If you don't want any control over sharpening, then Photo Enhance Pro is very quick for outputting a small for web reduction, but you have no other control & I don't find the end quality any better or worse than Reduce Photo Size.
I wish that QuickPic would offer sharpening control, but the developer doesn't seem interested, even though the app does do some sharpening of the image view of gallery images. Weird.
Overall, these photo app developers are NOT photographers & have little idea or care about the quality of the images & image outputs. They seem to be more interested in the software of the app just being somewhat functional. I get vague replies when I make suggestions about improving output quality that leads me to guess that they just don't give a &^% about quality, of both the app & the images. But still something is better than nothing. I just wish that they'd stop offering crap gimmicky apps with poor image outputs vs. something simple & of quality. I guess people just want to be entertained with crap eye candy even with a utility app?
If one uses QuickPic as your gallery app, then that may be the fastest workflow for resizing but to me the image quality is poor. If you don't use QuickPic, then my tests have shown that Reduce Photo Size is the best option so far & I've tried MANY apps in search of the Holy Grail.