Well for an average investor, bonus and split will look one and the same, as number of shares increases, while keeping overall value same, but from accounting perspective there is a difference.
For bonus issue, company uses it free reserves to transfer to equity. So in effect new equity capital is generated and distributed to shareholders by company. Why this are called as free shares? Because cost of aquisition of these bonus share is considered 0. (This is important only from taxation)
You can use this to delay the taxation or book some losses
This is true but only from face value point of view. So earlier if you had one share of FV rs. 10, after 1:1 bonus you will have 2 shares of FV rs. 10
However since this is just accounting entry there is no material change in business, so overall market value remains same and market price halves.
Still bonus is considered as positive because company is transfering its reserves to equity and sending out a message that in long term business is expected to do well.
Split is nothing but just splitting face value of shares. So If you had 1 share of FV 10, you get 2 shares of FV 5. Even cost of aquisition halves so there is no change from taxation perspective.
Hope this helps