I am looking at different tours, one does not stop to visit the city of Ayutthaya. will I miss alot if we skip this city?

instead we get a day trip into Myanmar.
which is best?

Is this a Thailand tour? If so, what is the itinerary? The Ayutthaya trip is from Bangkok. Presumably, the Myanmar trip would be from Chiang Rai. If that is the case and you are not going to Siem Reap, Cambodia on this trip then do Ayutthaya - preferably going by bus to get there and returning by boat on the Chao Phraya River. The Ayutthaya trip usually includes a visit to the Bang Pa In Summer Palace, a worthwhile stop.

craig is correct as usual...

i would just add this....it all depends on how much you you like ancient ruins....i personally found them a bit of a waste of time, but i did enjoy our stop at the summer palace nearby and the monastary across the river on an island---you get there by a small cable car...

i also do not think a trip across the river into burma is worth it...its just a town set up for smuggling and tourist junk...

there is plenty to do in bkk without leaving the city and also tons of shopping...

yes these are both tours, OAT offers a daytrip to Myanmar. Smartours goes to Ayutthaya.

Both tours spend time in Bangkok.

I do not want to miss Ayutthaya if it does offer amazing temples. Or would you consider this stop just more of the same stuff??

Ayutthaya is interesting but NOT amazing. On the other hand the day trip to Burma is set up for tourists and has nothing to do with the real burma. Neither, in my opinion, are make or break aspects of a trip. If you want to know which we think is the better itinerary let us see the full trip.