When comparing OI File Manager vs MiXplorer, the Slant community recommends MiXplorer for most people. In the question“What are the best file explorers on Android?” MiXplorer is ranked 4th while OI File Manager is ranked 9th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Few permissions
It asks only for Storage permissions. No other things are required.
Pro Lightweight
The app takes only a few seconds to download, as its size is only about 1.5 MB to download and installed (on MIUI) takes only ~6 MB full size.
Pro Open Source
OI File Manager is available for free under the Apache License 2.0.
Pro ZIP file extraction support
OI File Manager supports extracting ZIP files.

Pro Unlimited tabbed browsing and dual panel in landscape mode and drag and drop between panels also supported

Pro SAMBA, FTP, SFTP, WEBDAV, BLUETOOTH support
Pro Can do tasks in background
Things like pasting/moving files can be done in background.

Pro Extract and create compacted files
Extract and create 7z and Zip/Zip64 (splitted-encrypted), TAR, TAR.GZ, TAR.BZ2, GZIP, BZIP2 and extract RAR (splitted-encrypted, RAR5), XZ, APM, CAB, ISO, ARJ, AR, LZH, LHA, CHM, MSI, WIM, Z, CPIO, RPM, DEB, NSIS, LZMA, NTFS, FAT, VHD, MBR, SWM, MSLZ, CramFS, Dmg, ELF, MachO, Mub, PE, Split, Xar, Z, Udf, HFS, SquashFS, PPMD.
Pro Queue Tasks
Can Queue every task, copy, paste, move, delete , rename etc.

Pro Root access for all advanced operations
Pro Theming support
Download and apply a theme or easily create you own.
Pro Active forum support
Lots of guys giving pointers on the xda.
Pro Available for Android TV
Pro Multilingual
Supported languages of the main program: English, German, Bulgarian, Croatian, Czech, Chinese, Danish, Dutch, French, Greek, Hebrew, Hungarian, Indonesian, Italian, Japanese, Korean, Polish, Portuguese, Romanian,Tamil and many more.

Pro FTP/HTTP server built in
Share files trough the browser.
Pro Tasker
Automate tasks.

Pro All your cloud storage needs accessible from one single app
Choose from 19 providers:
Mega.co.nz, Dropbox, Box, Yandex, HiDrive, Baidu, Mediafire, Kuaipan, Kanbox, IDrive, Hubic, 4Sync, Google Drive, Copy, Meo, OneDrive, pCloud, SugarSync, VDisk.
- clouds which support webdav like (Yandex.ru, OwnCloud, MyDrive.ch, DriveHQ, CloudMe, CloudSafe, ...).
Cons
Con No additional features (suite)
No other features such as networking connections, junk flies cleaner, built-in media player/viewer/editor. But that might be a pro, since nothing else is asked for this app permission.
Con Outdated
At this moment I'm writing, it was updated last in 2017.
Con Ugly UI
The GUI is old and deprecated. But what would you expect for such a small app?

Con Not on PlayStore
The developer has chosen to not place the app on the Play Store but to offer it for free on the XDA forums. This may be inconvenient for some as the app will have to be side loaded.
Con Image browsing
Image browsing has bugs.
Con Search
Search doesn't work in landscape mode.

Con Buggy sometimes
Con Some features are not free
