Hi. I want to replace my hpi pulse transmitter and receiver with a better performance one.

Im saw Sanwa M12 and Futaba xp4.
Price for both is same. But not sure which one is better.

Not sure there is a "best" radio system on the market. There are a bunch of good ones, a few bad ones, and a bunch in the middle. I personally use a RadioPost system, and have no issues with it. It's fast, it's reliable, and it has a bunch of features I actually use on it. There are better systems, and there are worse systems out there.

Set a budget, and buy the best one you can afford.

Personally, I would stay away from Spektrum....but I had bad experiences with the DX3R I was running awhile back. Great radio at most tracks, but seemed to get interference too easy at other tracks for me. The new stuff might be better though as I know a bunch of guys running em without issue.... After swapping I realized that Spektrum felt slow compared to Radiopost for me.

A lot of it is once again user preference.

FUTABA 4PX with out a doubt best radio i have ever owned, and I've owned them all.

I own a Graupner X-8N that I got from Tower Hobbies. You can pick it up for less that $250 and is a great radio. Team it up with their servos and you can get super low response times.

I like my futaba 4px but it's always split 50/50 between that and the m12

Get the one that fits better in your hand.