Looking to replace the SSD I have in my system now, and I am between both of these options. I've read good things about both, I have heard the PRO is overkill, and I have heard the PRO is a noticeable winner. Bottom line: I'm using it for gaming, and if I can't really notice the difference with boot time's and gameplay, I'd rather have the extra space, and vice versa. Prices now are $120 for the PRO and $130 for the MX300 525GB. Open to all suggestions.