I would say that the hosting plan/server has a significant factor for the speed at which the galleries will load. Same goes for the videos playing.
Another big factor is the coding behind the scenes that load them.
Example: my original flash video player rendered and cached the on-site videos much better. However, a decision was made to keep the layout uniform … so I went with a different flash video player.
With regard to the gallery – these are the times I get, by no accurate measurement other than using my stopwatch feature on my mobile phone.
System: Toshiba R100 (1GHz 512MB RAM) Laptop w/ WinXP running Safari 3.1.2 on 512kb/s ADSL
With empty cache – Korea 2007 Gallery – ~12.4 secs for first picture to fully load, appears around 9 secs
With empty cache – Crash Test Gallery – ~ 9.2 secs for first picture to fully load, appears around 6 secs
With empty cache – Hobart 2005 Gallery – ~6.1 secs for the first picture to fully load
Re-entered – Korea 2007 Gallery – ~8.2 secs for first picture to fully load
Re-entered – Crash Test Gallery – ~5.8 secs for first picture to fully load
Re-entered – Hobart 2005 Gallery – ~5.4 secs for the first picture to fully load
I'm noting I got similar times for the Crash Test Gallery whether I picked the "simpleviewer" or the "autoviewer" (Sliedshow). The above Crash Test Gallery times were using the "autoviewer". On average, the "simpleviewer" is about 1 second faster. I did not test out the tilt or postcard layout.
Also note, that Firefox 3.0.1 had similar load times, however with much better results once the cache contained the images. Using Firefox 3.0.1 on average loads the gallery about 1 second faster.
So depending on which gallery you viewed, there could be a few other reasons for a "slow" load time. It would appear that maybe the larger the gallery, the slower it loads. The size of the first image may play a big factor also. Although considering that the first picture for Crash Test Gallery is only 46kB vs. 70kB for the first picture in Hobart 2005 Gallery – I think maybe not, after it's cached anyway. First picture in Korea 2007 Gallery is 57kB.
In conclusion, with the same environment and the same scripts – only using different pictures with different sized galleries, it would appear that the larger the gallery the slower the apparent speed.
I would be happy to hear of other sites/galleries and their load times for comparitive sized galleries.