Good day and Merry Christmas to all!

I am looking for opinions on which type of media is best for long-term storage of important business data like emails, tax files, Excel spreadsheets and Word documents, so a time frame of at least 5 years, preferably longer, is required.

Currently we use CD-R or CD-RW, but the amount of data is growing.

I always thought tape was the de-facto standard for long term storage, but lately DVDs seem to get a good rating.

How would external hard drives rate for long-term data integrity assuming the drives had a suitable length warranty?
I assume no warranty will cover the data on the drive though.

Obviously there are significant price differences between the different media and the hardware to drive it, but I am just looking at media reliability at the moment.

Thanks.