oh oh oh....
be aware: the Thai Smile schedule (all flights starting with digit 7) is not so reliable as is the TG-mainline schedule.....Thai Smile schedule is changing frequently and I bet you will see some changes till your departure date.
And product-wise: Thai smile can by no means be compared to Biz-section on a mainline (longhaul) aircraft (equipment).....If I had to chose from I would definitely go for the slightly higher fare with about 8-10 daily flight options....