BOOTABLE USB RECOVERY DRIVE questions.

I have a couple of questions concerning USB Recovery Drives such as can be created by AOEMI and MACRUM Backup programs. They have got my PCs going many times over the years. First ,does the Flash Drive have to be empty?I think I recall having to format the drive before use, so they cannot be used for anything else. Is this correct? Second, is the content of the Drive after creation the same regardless of what program has created them? If not, are there benefits to using one rather than another?

The reason I ask is that I have 3 such Drives, two Aoemi the other Macrium, and was about to create another using Aoemi following a system Backup now that the latest update has been installed. But is this a wasteful use of USB space if they are all the same, one as good as another? What is the minimum amount of space required. I think I remember it being about 8 MB? If so it will not be an efficient use of a Drive much larger than that, if it cannot be used for other files.

It is good practice to use an empty drive,adding other programmes may cause issues.
Use one drive for one method,i.e. avoid putting Macrium and Aomei on the same stick.The sticks are cheap and for the recovery situation why complicate it.
Whenever e.g. Macrium updates,wipe the old recovery drive and make a new one.

Ztruker said:

When you create a USB flash drive from Aoemi or Macrium, the drive is wiped before it is written to so anything on it is lost.

I don't know about Aoemi, but Macrium does not normally wipe the drive. If the drive is already Fat32 and has about 1GB free space then it just add its files to what is already there. Formatting the drive is only done as a last resort.

Rescue Media Builder will first attempt to non-destructively copy the PE/RE files to an existing partition, then non-destructively create a new partition if necessary. If this is not possible then you will be prompt to destructively format the drive.

Creating rescue media - KnowledgeBase v7.2 - Macrium Reflect Knowledgebase

Or you can add multiple wim files to the sources folder and add the relevant bcd entries.

For example copy the sources\boot.wim file from macrium media to the desktop. Rename it to macrium.wim. Copy macrium.wim into the sources folder of the Aomei media.

Then add the bcd entries for macrium.wim. It is quite easy

Thanks for all the info and links. Where possible I will always take the more simple option. I find now that I only have 2 Bootable Drives, one AOMEI , one MACRIUM, neither have a lot of space which would 'go to waste' if (as seems best) they are only used for one purpose. What puzzles me is that AOMEI has used 2.10 GB out of 3.72 GB where as Macrium has used only 540 MB, half a GB out of 1GB. What explains this disparity? Presumably the Bootup programs must be significantly different? I don't use Macrium now to create BACKUP S(I found it difficult to follow, whereas AOMEI could hardly be simpler) but as the USB Drive MACRIUM is on is so small it rules out using it to create a fresh AOMEI Bootable. So the course of action I should take is to create a new Bootable on the 3.72 Drive, leaving me to think about what useful purpose I can find for a 1 GB Drive (a free give away with a magazine).