Is there much of a difference in the power draw between hibernate and suspend?
The difference is nothing (hibernate) compared to something (suspend)...
Hibernate means that the laptop writes a file as big as the amount of RAM to the hard drive which contains the exact contents of your RAM. When you restart (open the lid) that file is read & written to RAM. The end-result is your pc just like it was before you closed the lid to put it in hibernation.
Suspend is almost the same thing : your pc shuts down but the memory is still powered. When you restart, the machine "is back" much faster because it only needs to properly start all devices rather than start those devices AND reed a 256Meg (or 512Meg) file from the hard drive.
Have you looked at the DELL site for BIOS upgrades ? From personal experience I can only recommend visiting their often and always keeping your machine flashed up to date (but wait at least 2 weeks after a new version is released). Other known issues with suspend are add-ons like misbehaving (scsi) pc-cards etc. NAI's Sniffer PRO version 4.5 and 4.6 killed my laptop on suspend (fixed in 4.7) and open VMWARE sessions are also a definite NO-No.
Hope this helps...