Don't know if 4 ohm is better than no ohm.
I know that 4 dollars are better than no dollars.
no the higher the ohm the more resistance in the speaker the lower the resistance the more power it will use so if they are the same make the 4 ohm should be louder
Sorry, but there is really no 4 ohm or 8 ohm amplifier. We use only voltage bridging. Scroll down to related links and look at "Interconnection of two units".
You need to match the speaker with the amplifier. Better or worse is not the question. The question is dynamic range and the possibility of overloading the amplifier. If the amplifier is rated 4 ohms, use a 4 ohm speaker. Same for 8 ohms. Do not "mix and match".
You can, but the available power will only be about half of rated, and the frequency response will be slightly different. Better would be to connect two 8 ohm speakers in parallel, making an equivalent 4 ohm speaker.
For smaller values (eg below 1000), simply use ohm, for biggers (above 1000000) use megohm, between them use kilo-ohm.
There is neither 4 ohm nor a 8 ohm output of an amplifier. Less than 0.5 ohm is the output impedance of a loudspeaker amplifier. Scroll down to related links and look at "Voltage Bridging or impedance bridging - Zout < Zin".
2 in series with 3&4 in parallel
the impedance of a speaker is a characteristic that is has. A 4 ohm speaker will always have a 4 ohm impedance and it cannot be changed. If 2 speakers of 4 ohm impedance are wired in parallel, then the total impedance will be 2 ohms. Similarly, if you wire 4 speakers together, the total impedance will be 1 ohm. Wiring a 2 ohm speaker to an amplifier rated to drive a 1 ohm load should work without any problems but expect the total power output to be somewhat lower than with a 1 ohm load.
The impedance of the speaker does not determine its quality. Assuming that your amplifier can drive the 4 ohm speaker, you will notice that this speaker is louder than the 8 ohm one.
You can use your so called "4 to 8 Ohm's output" amplifier for your 10 ohms loudspeaker. All amplifiers have an output impedance of less than 0.5 ohms. You use impedance bridging when you connect the 10 ohm's loudspeaker. The "4 to 8 Ohm's output" means only that a 4 to 8 ohm loudspeaker will be adequate and not that the output impedance is 4 to 8 ohms! Scroll down to related links and look at "Impedance bridging - Wikipedia".
There is really no 4 ohm amplifier. The output impedance of a good amplifier is less than 0.5 ohms. Scroll down to related links and look at "Voltage bridging or impedance bridging - Zout < Zin - Interconnection of two audio units".
First, you must know: There is no 4 ohm amplifier. All audio amplifiers have an output impedance of smaller than 0.5 ohms. So you use impedance bridging. No problem to connect the 0.5 ohm output to your 4 ohm loudspeaker. Scroll down to related links and look at "Impedance bridging - Wikipedia".