You might be surprised, honestly.....
Also, regardless of the radio, get a new antenna.... The ones that come with the Uniden scanners is crap. Search around these forums for replacement suggestions.
Lastly, regardless of which model you choose, invest in the DMR and NXDN upgrades. You might not think there's much going on, but having these upgrades might surprise you.
As for the waterfall function, it's a great way to snoop around the bands for anything unexpected that's not necessarily in the database. It's great to have, but not an absolute necessity. (It also helps in seeing any interference to what you're receiving....)
(I have the SDS100, so I know this radio fairly well..... The 436HP is similar, but as I said, the biggest difference is the simulcast handling. Both have the aforementioned upgrades available, except the waterfall, which is on the SDS units only, as far as I know...)