Seldom does a company make 2 products that do almost the exact same thing, but Fluke's low end ampclamp (the 322) is almost a duplicate of the high-end digital amp-probe (T5) Fluke T5-1000USA,Electic Tester 1000V,Continuity,. Here are the big differences.
The 322 can handle BIG conductors and big currents (400A AC). The T5 maxes out somewhere around 3/0 copper wire and 100 A AC. The T5 has a bright red light to warn you when high voltages are present - the 322 warns you with an icon in the LCD display. The T5 comes in 600 and 1000 V versions, but the 322 is limited to 600 V.
The 322 works like the traditional amp-clamp. The T5 is best described as an "amp-FORK" because the opening is permanent and doesn't need to be closed to make an accurate measurement. The T5 "FORK" will accept a 1/2" diameter conductor but nothing bigger. You just poke it over the wire and the AC current is measured when the wire gets to the bottom of the fork. Neither model makes DC current mesurements. Consider the 337 if you need DC current. Also look at the 333 - it is similar to the 322
The T5 is smaller. about 1/2 the width. Both run for a long time on 2 AA batteries but the T5 runs twice as long. Using Lithium L91 AAs you can forget about batteries for a few years of everyday use.
The T5's probes are PERMANENTLY attached to the meter so they never get "borrowed". This may seem trivial but if you work around other people probes seem to be able to walk. They stow nicely in clips built into the T5 case or you wrap them around the 322. One T5 clip even doubles as an extended probe holder on the so you can use one hand to hold the meter and probe with the same hand, keeping you even further from the live circuit. At 1000 V that's a nice feature. The probes are removable from the end of the cables on the T5 so that you can put a clip on one line instead. The 322 accepts a full range of test accessories subject to it's 1.5 Megohm input impedance which can upset thermometers, or especially high voltage probes.
The T5 automatically switches AC or DC voltage depending on what it sees comming in and indicates it in the display as AC or DC. The 322 has a dial setting for AC or DC voltage and you must tell it which you want to measure. If you have a complex signal (AC+DC) ONLY the 322 can tell you about each part - the T5 will just pick one, usually the AC, unless the voltage is stable like from a battery or DC supply. Thus the T5 is somewhat ambiguous with combination DC/AC signals. These need a traditional DVM like the 179/279 series.
The T5-1000 can go to 1000 volts AC / DC, but the 322 stops at 600V. The T5 measures to 1000 Ohms, the 322 stops at 400 Ohms. Both have continuity beepers. The 322 goes to .01A resolution, the T5 is .1A
Those are the hard facts, here are some Personal Thoughts from using both:
Neither the 322 or T5 are a replacement for the traditional bench DVM like the 179 or 279 but they can do ALOT of basic electrical measurements fast and easy. They are GREAT tools if you need to make current measurements quickly without disconnecting the conductor and also want to measure voltages and wire resistances. Input impedance of the meter is 1.5 Megohms instead of the typical 10 Megohms of a traditional DVM, so some accessories are not compatible with either of these. Both have a hold button - very helpful when you dig for a wire and once found you can't see the display - just press hold, get your meter back and read it later.
I like the "fork" on the T5 - it's fast and gets into smaller spaces than a bigger clamp. If I were working on MCM series cables, the 322 would be the only choice though. I also got spoiled by the automatic DC/AC switching on the T5. Most of the time voltage measurements are not complex AC+DC and if they are you need a different meter anyways.
I did alot of work on a high power 60Hz to 50Hz motor/generator set for testing foreign powered devices - I always used my T5-1000 when probing inside the motor/generator control panel live because I could clip one lead to ground and put the hot lead in the meter's extended holder then use it one handed to measure voltages with one hand behind my back. Since the generator had a DC field coil, the T5 would switch automatically when I measured the exciter DC voltage instead of the AC output which was one less switch to mess with. Setting up the generator was very simple using the T5.
Summary: These two products are so close you need to evaluate the voltages, currents, and wire size you work with to pick one over the other. Beyond 100A or 1/2" diameter conductors you are automatically going to need the 322. Above 600V, The T5-1000 wins. *IF* you can use either, the T5 is a bit more convenient and fits the hand nicely. They are 2 different meters and have different personalities, but are priced close and duplicate alot of specifications making it a personal decision. I hope this info helps you pick the right one for your job. Either one is a quality product that will have a long service life. Oh yea, the T5 is spec'ed by fluke to survive a 10 foot drop - it is ruggedly built without an opening clamp mechanism.