if an electrical goods model is higher code compared to its previous model

does that always mean its a better version or has better specs then its previous model?

for example i brought a HP DV6000 series laptop, however you can buy a DV7000 series DV9000 series. on the other hand i found out DV6000 specs were better then DV9000 spec and they were both the same price?

so usually is it higher the model number of a products series the better?