Alittle more clarification-
The GRE's are still tied to a total of 22 scanlists or banks in working memory. So if you want to easily switch between lists of different trunked radio systems or fire, EMS, PD, busses, etc.; you are still stuck with 22 choices in working memory. Upside to the GRE's is you can put 1800 TG's or frequencies in 1 scanlist if you like.
All the DMA Unidens with the exception of the 246T have 99 systems available for use. So you can have 99 different classifications-i.e. you can have 99 different agencies, or split up your agency into 99 different sub-categories. Downside to Uniden is that you are held to either 200 or 250 TG's/system depending on the radio.