Right commercial oven for Frozen Foods?
The Rational oven is definitely more flexible - it usually offers a dry and a wet oven capacity. If you're reheating any wet ingredients like pasta, rice, sauces, you'll find the merry chef very unsuitable.

Options 2 and 3 that you've listed are good for far reheating of relatively small numbers of portions that need heat + crisp eg pies, roast potatoes. But they're not so good for wet foods or large batches