Welcome Monica!!
Over the years, I've had two ceramic kamados (a 14" Visions, and an 18" BGE), and two metal kamados (an 18" Broil King Keg and my current one being the Summit - 24").
My key experiences...
1) After having a 24" grilling surface to use, I would never go back to an 18". So many more options for cooking open up. I usually only cook for 2 people as well, but when party time comes...24" is it! If you ever plan on smoking larger volumes of food - two briskets, 4-8 racks of ribs, 4 pork butts, etc....the 18" will make you unhappy. If you want to grill 7-10 steaks, 20 burgers etc....18" will make you unhappy...etc. etc.
2) So, assuming point 1) is valid for you, then I went to $$$. If money was no object at all, it would be a tough choice between the Kamado Joe Big Joe III, and the Summit as both take care of the 24 vs 18 thing. But the problem is, the Kamado Joe is lot more $$. So, you have to price them out yourself and make a decision based on that too.
3) Fuel. You can use both briquettes and lump charcoal on the Summit...it happily burns both. The ceramics seem to prefer the lump charcoal and not work with briquettes properly. Not that big a deal IMO, but briquettes are cheaper, and burn nice and even etc. I personally use both (depending on what I am doing), and even mix them together.
4) Horizontal Grilling. The Summit, with both the lower and upper charcoal grates, can hybrid grill as a kettle and you can spread out coals on the top grate to get a very large grilling area and grill an absolute ton of hamburgers, steaks etc... Ceramic kamado design is more vertical and hard to do this on. All the heat tends to be center focused and food on the edges do not sear...so you are moving things around to cook evenly.
4) Weight. Do you need to move it around much? If so, you are going to have a bad day with the ceramic.
5) Temp control. The Summit is better at varying temperature - both up AND down. Ceramic grills are tough to lower the temps on once you hit them. If I had to pick a stability champion, I would say the ceramic is better than the Summit because of the greater mass, but not by much,
To me, those are the biggies....I would be happy with either from a cooking standpoint....I was NOT happy with the price of the KJ. I absolutely LOVE my summit. Cook on it so often here....