The PowerLogic ION7550 and ION7650 each have a different feature set:

ION7550: revenue-class power and energy metering, event and min/max logging, historical logging (up to 800 channels), expandable memory, sag/swell monitoring, harmonics measurement, waveform capture at 256 samples/cycle, setpoints, digital and analog I/O, and Internet-enabled multi-port communications
ION7650: adds symmetrical components measurement, fast transient detection, waveform capture at 1024 samples/cycle, and power quality compliance monitoring.
Characteristics (some features are optional):
Panel-mount, large customizable LCD display, available without display
Multilingual support for English, French, Spanish and Russian. User-configurable IEC or IEEE notations. 12/24 hour clock support in multiple date/time formats.
3-phase, 4-quadrant metering, class 0.2 accuracy (IEC, ANSI)
Voltage, current, neutral and earth current, power, frequency, power factor, demand, energy, and time-of-use metering
Instrument transformer correction, transformer/line loss compensation
IEC 61000-4-30 class A ed. 2, IEEE 519/1159, EN50160, IEC 61000-4-7/4-15 power quality compliance monitoring
1024 samples/cycle waveform capture, transient capture (20 μs @ 50 Hz), sag/swell monitoring, harmonics measurement (up to 63rd), symmetrical components
COMTRADE waveform format available directly from the meter
Disturbance direction detection to indicate whether a disturbance originated upstream or downstream from the meter
Setpoint learning to automatically learn what constitutes a sag, swell, transient or high and low setpoint
Sequence-of-events, coincident minimum/maximum, historical trends, and high-speed snapshot recording, 1 ms resolution timestamping, GPS time synchronization
4 analog inputs, 4 analog outputs, 16 digital status/counter inputs, 7 digital control/pulse outputs
65 setpoints for alarms and control, 1/2 cycle response, multi-condition, call out on alarm
5 communication ports: Ethernet, modem, RS-232/485, RS-485, front panel optical
100Base–TX and 100Base–FX for faster Ethernet communication
Protocols: Modbus RTU slave/master, Modbus TCP, DNP 3.0, MV-90, IEC 61850
Ethernet and modem gateways to 31 devices on RS-485 port
On-board web server, email for alarms and data, FTP server

Watch: ION7650 Power Quality Meter: Transient Detection