In Windows as far as I remember there is no 1 Gb ram phone with snapdragon 200 processor.
1 Gb ram phones are useful if you are a gamer, otherwise 512 Mb ram will do the job. Processor in Windows phone doesn't matter much as windows phones doesn't lag even with dual core older processors. So at the end its upto you to buy a phone with 1 Gb ram or with 512. According to me 630 is good for 512 ram & 730 is good as a 1 Gb ram phone.