I quite like its simplicity though it could do with some sort of progress meter.

The main reason you wouldn't use --lzma with UPX is for speed; NRV is faster. Although both tend to be so fast it doesn't matter, the size difference also usually doesn't matter.

Oops, in the interest of staying on the topic of this freeware app, I should probably mention I haven't... erm... used it. X_x

But my main source of hesitation is the obscurity. Most reasons for compressing files are for other people to easily download and use later. And most people want convenience, which is why you package all the files into one container in the first place. They don't want to get some decompression software they've never heard of.

A portable decompresser like this sorta overcomes that partially, and it might still be useful in some scenarios. Depends how DESPERATE you are for a few extra KB.

ZIP compression has an advantage with text-based formats (txt, possibly chm and hlp) since it was made with text formats in mind. I don't know what RAR was made to handle originally.

At any rate, file size is less and less of an issue these days as broadband and bigger hard drives become more ubiquitous. Everyone can handle ZIP, even fresh-off-the-CD Windows users. Not to mention that most formats have a self-extracting mode to bundle the extractor with the archive, which makes it even easier on people.

I myself use 7-zip because:
- The tool itself supports many archive formats so I don't need 100 different tools.
- It has both GUI and CLI versions. The CLI EXE is great for compressing 100s of files each into their own archive with the FOR command. Gotta love the command prompt.
- 7-zip format is better than zip in most cases.*
- Has a shell extension menu for compressing/decompressing.
- Is 100% freeware, yummy!

* - Even with UPX I use the --lzma compression mode (ie the same 7-zip uses) and I find it consistently gives better ratios than even --best does. Sadly whenever I find a UPX compressed EXE or DLL I can always get it smaller by unpacking it and using --lzma... makes me wonder why people don't use it. I guess they don't know? Only times where --best (or ZIPping on generic files) gives better ratios for me usually is usually on very small files where it doesn't matter much anyways.

ZIP (Deflate compression) is more stable on already compressed data compared to the RAR's algorithm.

RAR compression worse than ZIP?! You can't be serious.

your results with zip better than rar is very very debateable, zip is one of the worst old time archaic compressors avail, surprising results nonetheless.

i tested a 75.1 MB file (over 4,000 files), with txt,dll,exe,jpg,gif,ico,zip,bmp,wavs,chm,hlp,bin files, and heres the results.. with

RAR: 37 MB
ZIP: 34.9 MB
PEAZIP: 34.9 MB
TAR.GZ: 33.5 MB
TAR.BZ2: 32.0 MB
PIM: 31.3 MB
7ZIP: 22.8 MB
PAQL8 (had to quit before it used up all my memory, so i couldn't get proper results)

Forgot to mention the result using paq8l:
http://www.cs.fit.edu/~mmahoney/compression/paq8l.zip
1 folder 61 images @ 17.3mb
paq8l = 13.4mb

Usage is simply drag and drop your file or folder onto the exe file to compress, and the same to uncompress the paq file. Much slower than pim and 7zip but its one of the best compressors avail.