At that price, as long as it in good condition, I would get it if I were you. BUT... only if I had played an S910 first.
There's a difference between technology and 'sound'... the latest technology doesn't necessarily mean the 'best' sound. Roland's and Yamaha's seem to come from almost two different planets!
IMO, Roland have a VERY punchy 'in your face', live band sound. Yes, it's heavy, but the reason for much of that is firstly, a BIG, smooth, fantastic feeling, semi-weighted (by that, I mean a cross between standard good plastic keyboards - MoXS, M3, FantomG, etc. and fully weighted piano actions), great feeling action, quite definitely the BEST plastic action I have ever played... piano shaped blacks, but smoother shaped whites, so good for piano AND organ (most piano actions catch your hands on the whites doing smears on organ). Highly recommended (if action makes any difference to you).
Advantages to the S910 come with a MUCH better guitar section, and some very nice lead sounds, SA sax particularly good. Piano I would give a BIG edge to the Roland, though. Unless you like overly bright, thin piano sounds. I tend to like warm and detailed at low velocities. The Yamaha stays bright and cold even at low velocities.
Styles tend to be busier with Yamaha, very full and nicely done, but not so much room for YOU to play. They tend to 'do it all for you' stuff, whereas Roland styles leave a bit more room for you...
The Roland is expandable, and I would recommend adding an SRX board at some point. There's a couple with some GREAT sounds you might really like.
Yamaha's technology is definitely more advanced than Roland, but other than the guitars, in a style, it's not that big an advantage. The sound, and once again, this is MY opinion (but shared by many that don't play Yamaha!), it's a bit on the bland side, very smooth (for a good adjective) and compressed (for a not so complimentary one!). More like listening to a CD than live musicians.
But with work, I am sure the S910 could be made more punchy...
Both keyboards are good. But at that price, the G70 is quite a bargain. Unless you have the same preference for ultra-lightweight action and CD compressed sound that some prefer, I'd go with the Roland. Some would have you believe that choosing Yamaha's MOTL arranger involves NO compromise. Less prejudiced posters might point out that the MOTL of ANY line is a compromise, but you'll seldom hear that from those that use them...