@For Jack
The only difference between the Confirm and the Micro are the size of the meter itself. They both take the same sample size and use the same strips (which you can also buy at ADW for $69.99 for 4 boxes of 50 with 1 free box....so 250 strips for $69.99...and they occasionally send you emails with coupons worth 10% off an order and/or free shipping on any size order)
The Micro is a smaller unit, so handy if you're carrying it around in your pocket all day (not so important for our kitties as it is for humans) The Confirm is a little bigger unit, so better if you have trouble holding smaller objects (like if you have arthritis in your hands)
Both take the tiniest size sample possible and generally they're very reliable. If you started getting wonky numbers, you might want to replace the battery or if you call Relion, they can send you control solution you can test with...and they're also pretty good about replacing any meter that's causing problems so you don't necessarily have to buy a new one.
The Prime takes a larger sample size (not a lot larger, but larger..... 5 microliter versus the Confirm/Micro that only takes 3 microliter)
The other thing I've heard quite often is that the Prime tends to give more error messages if things aren't "just right". I found this true when I tried it, but some people have absolutely no problem with them and the price savings on the strips is pretty nice. The Prime has boxes of 100 for $17.88 where the Confirm/Micro are $35.88 for 100. You can get boxes of 50 for $9 for the Prime (they also have smaller boxes for the Confirm/Micro)
Remember, ALL meters can be off as much as 20% ....even on the same drop of blood!! So if the first test you get is a 500 and you immediately retest, you could get anything from a HI (over 600) to 400, so it can be over 200 points difference and still basically be the same number. The important thing to remember here is if it's too high, it's too high...it really doesn't matter a whole lot if it's 300 or 500....both numbers are too high and doing damage to the kidneys and other internal organs.