Is there a problem creating only differential backups every hour? I have three databases which are not big. Every differential backup is roughly 50MB, then we have a full backup at midnight.

Is there any problem doing this? 

I could take the full backup then logs, then diffs like 4 or 5 times a day, but storage is not a problem with this instance. I can afford to lose 1 hour of data, that's no problem, that's why I'm creating all of the diffs (I'm using full recovery mode). Then I can restore only the full + diff , instead of full + log + log + log + log + log + log + log
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Storage is not why you take log backups.  You take log backups when the database is in full recovery model, and you need point-in-time recovery between full or incremental backups.

If your business can afford only 1 hour of lost data, then I'd typically setup nightly full backups for smaller databases, with log backups every 30 minutes during business hours (or even 24-hours per day).

If you had the database in simple recovery model, and each database was only a couple of hundred megabytes, you could simple take full backups every hour, or half hour.

Essentially, the decision comes down to answering these questions:


What is my recovery point objective?
What is my recovery time objective?


See Wikipedia for great details about what those two things actually mean.

If you're storing high-value, business-critical data in those databases, you should understand log backups, and the transaction log and recovery in general (link to my blog), to avoid being in a situation where you're unexpectedly missing data, or down for an extended period of time.

In your case, I would also do a log backup after every diff backup just to ensure the log doesn't grow out of control.