If you compare a sports car with a lorry there are quite a few differences. And the Tannoys are more like a sports car and a large Meyer system is more like a lorry. If you want to deliver sound to 10,000 listeners in an arena I would select the Meyer Leopards above the Tannoy Eatons anytime. But it would be a very unfair comparison, the Leopards would not work very well in my living room.
So let us make a few things clear first. Audiophile equipment is made to be bought by audiophiles. Professional equipment is made to be used professionelly, that is earn money. This means that sometimes audiophile equipment contains functions or solutions that might not really add anything to the sound quality but add to the buyer perception of getting something unique or special. On the other end, professional equipment is made to be functional and robust and simply delivering up to requirements and these might or might not include "fidelity".
Let us look first at PA equipment. This is more like the lorry size equipment. If you go to an arena size event you will find that one of the main requirements is to be able to deliver enough dB to the audience. This can be done with different levels of "sound quality". You can get hifi quality on a full arena using the correct tools. On the other hand, if all that is required is to be able to hear a voice announcement you will use quite different tools. This distinction is the actual point of professional equipment -- it is a tool to reach a goal and the goal varies with the circumstances.
A much fairer comparison would be with studio monitors. And incidentally, various generations and models of Tannoy speakers has been and are used as studio monitors. The general goal of a professional studio monitor is to allow an engineer to make the correct decisions when mixing or mastering. Most studio monitors are made to as faithfully as possible reproduce the sound, not adding or removing anything. A few studio monitors, say mixcubes, are for specialized use but we may disregard these here. The first question to ask when selecting studio speakers is about the size of the room and the listening distance. Even in a fully treated room you would use difference speakers for a 3 feet distance and a 10 feet distance. In a small room there is often not much use trying to listen to the lowest frequencys at all, the room simply "cannot take them". In a less treated room it is much better to listen close to the speakers to actually hear the sound.
So back to the Tannoy Eatons. They are passive, 30 liter two way ported speakers. When I read the specifications, there are no measurement curves which is a bit suspicious. The only measurement given is "40 Hz - 30 kHz ±6 dB" which would be considered on par with some well-known studio monitors but I would be suspicious on the lack of other measurements. As example the Neumann KH310 shows "30 Hz - 22 kHz ±6 dB" but also gives several measurement curves (those are powered speakers though). In the critical range 100Hz to 10KHz they are ±1.1 dB, the Tannoys give no value. Given the size of the Tannoys I would say that they would fit, probably quite well, in a mid-size room with a listening distance of slightly shy of 10 feet if the room is well treated. If the room is not treated I would most probably go with much smaller speakers, say between 4 and 6 inch woofer and listen at about 3 feet to not get too much bad influences from the room.
So to try to answer your question. "In terms of accurately reproducing an instrument or voice sound how do big professional speakers like Meyers compare to audiophile speakers like Tannoy Eatons?". My general suggestion is that a properly selected, installed and tuned Meyer system will reproduce voices and instruments really well, as would a Tannoy Eaton system in a properly treated listening room. In the wrong room or in the hands of the wrong user all bets are off and they might both be way off.