You're comparing storage (250 GB HDD) vs. internal flash + peripheral (4 GB model + Kinect). Note: "4 GB RAM" is incorrect — Xbox 360 has 512 MB RAM; "4 GB" refers to the 4 GB internal flash model.
Buy an Xbox One S (500 GB/1 TB) or Series S (512 GB) — backward compatible, faster, supported, cheap used.