I bought the 400 but If I had it to do over I would get the 300. It is basically the same machine less 2khz in freq. With the 400 I had to buy the small coil which I prefer and it does not make it so nose heavy. The 300 comes with the nice small coil. The Iron feature on the 400 is just not worth the extra money in my opinion. Good luck with yours, head for areas with fairly good soil for best results.