this depends
This depends on your needs or requiremens.
Are these all your domains, or your customers?
The reason I say this is our company like some other hosting companies offer both regular hosting and reseller hosting BUT both of our reg hosting and reseller hosting you can actually host "unlimited domains" on either plan!
You will have to 1st determin what your need are and how much you want to spend per month.
For example we have a few customer who host 50 sites within their one domain account and choose to only pay $5/mo.
They are farily small sites, but works well for them.
If you are more interested in having your own web hosting company & want more options and total 100% control of all of your sites I do recomend having your own reseller hosting account.. this way you can trouble shoot emails, restrict & monitor each account, control bandwidth and megs and much much more.