It's a question, I have never had these and would like to know people's thoughts.
I have used these and got them in for other people.
My opinion is stick to UK ratpaks.
The US MREs are not particularly impressive, they only do one meal, are packed with additives and are very pricey for what they are. UK rats are much better value, usually in date, more varied and can actually be classed as real food! Ratpaks have really improved of late. You can easily buy the chem heaters if you want to play with those, they work with any foil pack meal.
You can try MREs out of interest of course but most people I know reject them long term. For the price of one MRE you can have a better ratpak that is for all day.
Just my 2p worth