Rabbit or Standard Vibes
Which is better depends totally on the person. Some women can only get off if their clit is stimulated; others love the feeling of being penetrated. If your girlfriend usually comes during oral sex and not vaginal sex I’d say get her a pair of vibrating panties or something like a clit pump or the soft touch clit licker. If she seems to come with both a rabbit vibrator is probably right up her ally. The biggest benefit of the rabbit style vibrator is that you get the clit stimulation at the same time you get penetration. A standard vibrator is good just for penetration and stimulating the g-spot.
I have a rabbit style vibrator and swear by it, mine is the Gyrating Beaded Dolphin. It has every option you can think of and then some. It has dual speeds for the shaft and the clit stimulator, various different pulsating rhythms, and to top it all off the control pad glows in the dark so there’s none of that fumbling around right when you need to change the speed or something.