[Rob1968]

I was kinda rushed when I made the OP - - I had to get to work, and then back to the tournament, in the afternoon, for some finals, in the early afternoon. Thanks, for all the input.
The game in which the play occurred was good quality JVB game in a tournament.
As Lead, on a freethrow, the ball bounded high off the rim, to my side, and B2 and A2 got some good air, grasped the ball, with enough momentum that when they came down the one player's foot was on the endline. I expected that as they landed, one or the other would demonstrate more control of the ball, and was thinking that the oob call would be certain. However, they both still had such a grip on the ball, that neither could wrest control from the other, (without excessive rough play), and the held ball call became my choice.
As stated by several of the respondents, in most cases, the oob call would be the easy, preferred call. I posed the question because of the rarity of the elements of this particular play that led to my call.
(Incidentally, Rob 1968 refers to the year in which I officiated my first inter-scholastic game. So Mark Sr.'s got nuthin' on me when it comes to years in the rearview. . .)
Also, my use of the term "jumpball" may seem antiquated, but when I hit the whistle on a heldball, I usually verbalize "Jump!", in keeping with NFHS Officials Manual, 2.4.3 C. It seems to help with managing the possibility of excessively rough play.