What is your network connection though? GPRS, Edge, 3G or Wi-Fi? Any of the first two are going to be slow(er) - GPRS in particular, 3G varies depending on the load from other users on the network at the time but should be reasonably fast and Wi-Fi should be fastest.

It's a wifi network, and my signal strength is fine, seeing as in the above tests I was about ten feet away from the router.

You might compare the speed of syncing using Bonjour. If it's significantly faster (which I would expect!), then the bottleneck is either your Internet connection (unlikely) or your WebDAV service provider (Box.net, in this case).

I also have like 167 zip files on my WebDAV server (as reported from iPhone). Syncing is fast on the mac but slow on the iPhone. I checked that I have only these two in my preferences and also that they have been synced recently.

However I see some strange behaviour in the Apache Logs auf the WebDAV server:

This is the Mac syncing - everything fine. It gets a 401 first to authenticate and afterwards seems to be doing the sync normally (note there are more similar entries in the log).

[CODE]128.141.131.166 - - [14/Sep/2009:16:45:30 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus HTTP/1.1" 401 465
128.141.131.166 - dka [14/Sep/2009:16:45:30 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus HTTP/1.1" 301 329
128.141.131.166 - dka [14/Sep/2009:16:45:30 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus/ HTTP/1.1" 207 467
128.141.131.166 - dka [14/Sep/2009:16:45:30 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus HTTP/1.1" 301 329
128.141.131.166 - dka [14/Sep/2009:16:45:31 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus/ HTTP/1.1" 207 49970
128.141.131.166 - dka [14/Sep/2009:16:45:31 +0200] "PUT /dav/dka/omnifocus/OmniFocus.ofocus/20090914144747%3Dno9MYrve6L4%2BgHYX51p1ipQ.zip-write-in-progr
128.141.131.166 - dka [14/Sep/2009:16:45:31 +0200] "MOVE /dav/dka/omnifocus/OmniFocus.ofocus/20090914144747%3Dno9MYrve6L4%2BgHYX51p1ipQ.zip-write-in-prog
128.141.131.166 - dka [14/Sep/2009:16:45:31 +0200] "PUT /dav/dka/omnifocus/OmniFocus.ofocus/20090914144819%3DgHYX51p1ipQ%2BnfYw1Wg8pOe.zip-write-in-progr
128.141.131.166 - dka [14/Sep/2009:16:45:32 +0200] "MOVE /dav/dka/omnifocus/OmniFocus.ofocus/20090914144819%3DgHYX51p1ipQ%2BnfYw1Wg8pOe.zip-write-in-prog
128.141.131.166 - dka [14/Sep/2009:16:45:32 +0200] "PUT /dav/dka/omnifocus/OmniFocus.ofocus/20090914144841%3DnfYw1Wg8pOe%2BnqdBBs7ohf5.zip-write-in-progr
128.141.131.166 - dka [14/Sep/2009:16:45:32 +0200] "MOVE /dav/dka/omnifocus/OmniFocus.ofocus/20090914144841%3DnfYw1Wg8pOe%2BnqdBBs7ohf5.zip-write-in-prog
128.141.131.166 - dka [14/Sep/2009:16:45:32 +0200] "PUT /dav/dka/omnifocus/OmniFocus.ofocus/20090914144850%3DnDYGc4IBUO8.client-write-in-progress-nuUDAF0
128.141.131.166 - dka [14/Sep/2009:16:45:32 +0200] "MOVE /dav/dka/omnifocus/OmniFocus.ofocus/20090914144850%3DnDYGc4IBUO8.client-write-in-progress-nuUDAF
128.141.131.166 - dka [14/Sep/2009:16:45:32 +0200] "DELETE /dav/dka/omnifocus/OmniFocus.ofocus/20090914124616=nDYGc4IBUO8.client HTTP/1.1" 204 -
[/CODE]

However if the iPhone is syncing, it looks like the following. There's a 401 for each request and only then the iPhone is authenticating (dka is my username here, 3rd column). Something seems to be strange with the session handling and/or authentication here (although here: there are more similar entries in the log):

[CODE]
128.141.72.107 - - [14/Sep/2009:16:52:21 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:21 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus HTTP/1.1" 301 329
128.141.72.107 - - [14/Sep/2009:16:52:21 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus/ HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:21 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus/ HTTP/1.1" 207 467
128.141.72.107 - - [14/Sep/2009:16:52:22 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:22 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus HTTP/1.1" 301 329
128.141.72.107 - - [14/Sep/2009:16:52:22 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus/ HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:22 +0200] "PROPFIND /dav/dka/omnifocus/OmniFocus.ofocus/ HTTP/1.1" 207 52294
128.141.72.107 - - [14/Sep/2009:16:52:23 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144017=hkc9yI5EEWs+gxj7p61CU06.zip HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:23 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144017=hkc9yI5EEWs+gxj7p61CU06.zip HTTP/1.1" 200 2737
128.141.72.107 - - [14/Sep/2009:16:52:24 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144016=hy0P2YIrUdp+hkc9yI5EEWs.zip HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:24 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144016=hy0P2YIrUdp+hkc9yI5EEWs.zip HTTP/1.1" 200 3835
128.141.72.107 - - [14/Sep/2009:16:52:24 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144857=nqdBBs7ohf5+jGWXisb_CdN.zip HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:24 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144857=nqdBBs7ohf5+jGWXisb_CdN.zip HTTP/1.1" 200 650
128.141.72.107 - - [14/Sep/2009:16:52:24 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144910=d3zfkShq_cJ+cVcdehSRygQ.zip HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:24 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144910=d3zfkShq_cJ+cVcdehSRygQ.zip HTTP/1.1" 200 810
128.141.72.107 - - [14/Sep/2009:16:52:25 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144111=huHnlhvFoRj+no9MYrve6L4.zip HTTP/1.1" 401 465
128.141.72.107 - dka [14/Sep/2009:16:52:25 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144111=huHnlhvFoRj+no9MYrve6L4.zip HTTP/1.1" 200 2736
128.141.72.107 - - [14/Sep/2009:16:52:25 +0200] "GET /dav/dka/omnifocus/OmniFocus.ofocus/20090914144904=jGWXisb_CdN+d3zfkShq_cJ.zip HTTP/1.1" 401 465[/CODE]

Maybe this is also part of the reason why the sync from the iPhone is so slow. I guess making almost double the requests necessary is a significant performance loss (at least on mobile networks). (NB This was WiFi)

Used versions: OmniFocus 1.7.3 on the Mac, 1.5.2 on the iPhone