When us bouncers used to informally train (beat the hell out of each other) we tried to use what was as close to the real thing as possible. This way IRL the "mechanics" are the same, the real gun and dummy gun wil throw the same distance, hit equally as hard in a pistolwhip/barrel thump.....etc.
So my recommandation is to get a blue gun, it may hurt a little more at times but to quote a famous shrink "that which does not kill us makes us stronger".
And to add my 2¢, I would only train with a real gun IF, and only if, it had one one bright yellow polymer barrel inserts. There is no chamber, so even if live bullets were used in the clip to fully simulate weight a round COULD NOT MYSTEROUSLY FIND ITS WAY INTO BATTERY. The one slight, and extremely narrow debateable advantage this would allow is to train the possibilty of pushing/shoving the slide back in a gun grab, then gripping it with hells fury while you try to finish getting the gun out of the opponents hand. By pushing it out of battery, usually as little as ¼" will keep the weapon from firing. It has happened IRL, more often than not purely by luck, but it can and does happen.

-Bill Liptak