Things to think about:
USB charging voltage is 5 volts, so 'USB radios" have 3.7 volt battery packs
Most of the 'better' radios (IMO) have 7.2/7.4 volt batteries.
What difference does it make?
The energy stored in the battery is the product of the milli-amp-hour capacity and the voltage
The M-25 USB radio has a 1500 mAH (1.5 Amp Hour) battery and the radio draws 2.3 amps on high power transmit. (lower voltage, so more amps needed to get that 5 watt output....watts=volts x amps) So in theory (not in practice- you probably will have less) you have 0.6 hours (36 minutes) of high power transmission capability, IF you haven't been using your radio to 'listen' at all.
My favourite Icom radio is the M-88 which is discontinued and has been replaced by the M-85 (go figure on the numbering system....).
The M-85 has a 2010 mAH 7.2 volt battery and draws 1.5 amps on high power transmit. In theory you will have 1.3 hours (78 minutes) of high power transmit time with the M-85
The Standard Horizon HX-40 has a 1850 mAH 7.4 volt battery and draws 1.6 amps on high power (6 watt) transmit. So that means in theory that you have 1.16 hours (70 minutes) of high power transmitting time.
In a rescue situation, which would you prefer?
The HX-40 and the M-85 (and M-88 before it) are nice 'short' radios so the antenna isn't up your nose when the radio is in the PFD pocket.
I'd be happy with either of them.
I'd buy a spare battery pack and an AA battery holder, probably, for taking on trips. Keep the radio charged up for emergencies. A good modern battery will stay charged for months.
I carry a spare radio on trips - the 'tent radio' for listening to the weather.