which is better and why?
*Effects, live usage, display, pads, sound*

Which one is better for a start in hardware beatmaking?

biggest difference for me is that the 505 got graphic waveform editing and on the 404 you got to trust your ears. both are mad cool!

Both are dope, I prefer my 404 because of the simplicity but wish it incorporated step-write into the sequencer.

My 505 is for sale btw, inbox me for details..

To start out get the SP 404 because it will be newer, you will be able to find memory cards and its much easier to use. Once you have the basics of sampling, sequencing and recording your music you should then ask yourself if you need something more advanced or maybe you will still be happy with the 404. LOTS of people here only use the 404 and make awesome music with it. It's not the limitations of the 404 that will hold you back, but rather the limits of your own creativity. I've got the 404 and 505. I personally prefer to use my 505, but I will never get rid of my 404. If I was trapped on a deserted island I would be happy to be stuck with either machine

simple: do you want to work with a screen and menus or not

505's strengths - 4 track sequencer, graphical waveform editing, can resample one sample into complete octave with single button and can autoslice your drums and stuff.
505's weakness - lacks some effects of newer 404 model.

404's strengths - dont have to hunt for a used one and worry about if it works correctly, sx model has stupid amount of memory for sampling with SDHC card
404's weakness - sequencer is useless for most people, sx model doesn't have true lo-fi sampling, it only samples at single rate, doesn't have immediate melodic applications like 505's octave resampling mode, must be done manually, along with beat slicing.

Both are fine for live stuff and both are fine for making good music. It really depends on your style of making music and workflow, I think. I had a lot of productivity and fun on both machines. I'm not sure which one I'd pick over the other function wise! They're like two hot ladies...you'd rather just have them both at once!

thx for so many replies.
what do you think of mpc 1000? its sequencer and comparison to 404sx's?
is mpc worth of buying? ( too high price )

MPC Sequencer vs. 404 sequencer? No contest. MPC stands for MIDI Production Center. The sequencer is the bread and butter of that unit, my friend.