Going by a comparison of OTL data, French Indochina would be much wealthier. In the comparison graph linked here, I've left Cambodia out of this graph due to the outlier effects caused by Khmer Rouge rule. I've compared Laos and Vietnam to Tunsia and Jamaica, two other postcolonial nations which enjoyed a relatively peaceful twentieth century. The data is GDP per capita and total fertility rate between 1913 and 2013. By 2013, the mean GDP/capita for Tunisia and Jamaica is $9,315, but only $4,9375 for Laos and Vietnam.One thing we must keep in mind is, that with spreading of new agricultural and medical technologies there will be a population explosion in the colonies.
In 1920 France had 39 million people, Vietnam 16 million, Algeria 5,8 million and Senegal 1,5 million.
In 1950 France had 42 million people, Vietnam 29 million people, Algeria 8,8 million and Senegal 2,6 million.
In 1980 France had 54 million people, Vietnam 54 million (even after all devastation), Algeria 19 million and Senegal 5,5 million.
In 2010 France had 61 million people, Vietnam 97 million, Algeria 38 million and Senegal 12,4 million.
Now, demography is not a destiny, but even with minor economical development the colonies will have huge economic and poltiical influence compared to what they had in interwar era.
I see a marked difference in income, but evidence from this tool on whether French Indochina would be more populous seems inconclusive. The southeast asian conflicts certainly killed massive numbers of people, but might also have delayed the demographic transition by slowing economic development.