My contribution, I would change more variables, but it takes too long.

Default scene w/ a PowerFractal and One surface shader added.
Res: 640x480
Detail: 0.5
AA: 3
GI surface details: checked
------------------------------------------------
GI relative> 1---- 2---- 3---- 4----
GI sample:
1 Dots: 00:18s 00:50s 02:10s 03:30s
- Render: 04:06s 04:29s 04:50s 05:58s
- Total: 04:24s 05:19s 07:00s 09:28s
2 Dots: 00:26s 01:20s 03:00s 05:15s
- Render: 04:35s 05:43s 06:19s 07:34s
- Total: 05:01s 07:03s 09:19s 12:49s
3 Dots: 00:29s 01:38s 03:55s 06:55s
- Render: 05:06s 06:16s 07:26s 09:11s
- Total: 05:35s 07:54s 11:21s 16:06s
4 Dots: 00:33s 02:12s 05:01s 08:20s
- Render: 05:18s 07:04s 08:18s 10:07s
- Total: 05:51s 09:16s 13:19s 18:27s
-------------------------------------------------