precise cloud-images significantly larger than oneiric

See below for detail, but basically from oneiric released images to precise images, we've grown from root filesystem used of 762M to 973M. That is 27% size increase.

This compares what I found on
   ubuntu-oneiric-11.10-<arch>-server-20120108
   ubuntu-precise-daily-<arch>-server-20120202

The .img and .tar.gz files on cloud-images have grown also, but strangely it seems less. comparing alpha-2 from precise to last release of oneiric (20120108) shows:

-------------- | 11.10 | prec | %growth
amd64 disk.img | 218M | 228M | 4.8
amd64 .tar.gz_ | 207M | 217M | 4.6
amd64 file tot | 559M | 575M | 2.9
amd64 ebs df__ | 762M | 883M | 15.8
amd64 inst df_ | 655M | 823M | 25.6
i386_ disk.img | 198M | 210M | 6.0
i386_ .tar.gz_ | 188M | 200M | 6.3
i386_ file tot | 484M | 505M | 4.3
i386_ ebs df__ | 689M | 814M | 18.1
i386_ inst df_ | 582M | 753M | 29.3

(Note, precise df numers are from daily build 20120108, 1 day after alpha2)
'file tot' is result of 'du --total --one-file-system --apparent-size'.

I suspect that part of the discrepancy between instance and ebs is somehow related to how we populate them. In the build process, the instance store builds are done into a 1.4G filesystem, and then that is grown (resize2fs) to 10G before publishing to EC2. The EBS population script downloads the 1.4GB filesystem image, creates a filesystem on a 8G disk, then mounts it loopback and rsync's the data from the image to the new filesystem. (Essentially, mkfs is done on a 1.4G filesystem, and one is done on a 8G filesystem).

So i have the following separate issues raised from above:
 * why such a dramatic growth between 11.10 and 12.04 current
 * can we/should we get the EBS filesystem usage more in line with instance-store?
 * Why the change in increased usage of ebs for a given release-arch:
   oneiric-amd64: 16%
   oneiric-i386: 18%
   precise-amd64: 7.2%
   precise-i386: 8%