Long Answer here. Getting back to the original question: It depends on the VOLTAGE (V-mp) of your panels. For example:
If V(mp) of your "100 watt" panels is 18.1 volts, the current at rated power (standard test conditions, which are very "sunny") would be about 5.52 amps per panel. A "PWM" controller will disconnect and reconnect the panels many thousands of times per second, so that the average charging voltage matches your battery requirement (typically around 14.2 volts, or maybe 14.4 if you have programmed it to do that).
At 14.2 Volts charging Voltage, the maximum power into your battery pack under "standard conditions" is only 5.52 Amps times 14.2 Volts (not 18.1 volts.) That is only 78.5 watts. The rest of the "available power", about 21.5 watts, is all left in the panels (and un-utilized) during those moments of disconnection. That power is WASTED in comparison to a theoretical 100% efficient MPPT controller feeding hungry batteries.
If V(mp) of your panels is closer to your battery charging voltage, the percentage of 'waste' is smaller. If V(mp) is much higher and further away, the percentage of 'waste' increases quickly.
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With just one panel, the cost of an MPPT controller ($150 and higher) is not justified. But with 4 panels at this Voltage, a PWM Controller can give you only 314 watts in standard test conditions. In comparison to the rated power, you're really only getting a bit more than "3 panels". The "100% efficient MPPT controller" gets you the other 86 watts.
No MPPT controller is 100% efficient - the real ones are generally around 91-94% efficient at converting "panel power" (in lower Amps at High Voltage) into more battery charging Amps at lower battery charging voltage. In this scenario, with a decent real-world controller, you would get around 368 watts (I assumed 92% efficiency). Your "real world MPPT" gain, in comparison to the PWM scenario, is only 54 watts (about 1/2 panel).
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But there is another important factor which we should add into this scenario. 4 panels into a PWM controller, at 5.52 Amps each, is a total of about 22 amps. (And with a PWM controller, that's all the Amps you can ever get). But, if you combine your panels in parallel near the panel mounts (to avoid running 4 sets of very long wires down to the Solar Controllers), you will have 22 amps in the long wire - with substantial power loss in the wire. They must all must be wired in parallel.
With an MPPT controller supporting multiple panels, you can put panels in Series - doubling the Voltage at the same current (2 'parallel' sets of 2 'series' panels, or 1 set of all 4 panels in Series.) In this scenario all 4 panels in Series, you could have just 5.52 Amps in the long wire (at 72.4 Volts V-mp). My own MPPT configuration is approximately like that, with 4 slightly bigger panels (at slightly higher Voltage, slightly higher current) all in Series.
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The last thing I want to advise is: If your batteries will all be "full" before 2 PM with either type of controller, then it makes no difference (which one you use). You only need MMPT when you need to squeeze that last 15-25% from your panels, or when V(mp) of your panels is much higher than your battery charging Voltage.