Is the regular Tennison gambit or the ICBM variation better?

If you plan to play time control's longer than Bullet and Blitz (i.e. Rapid and Classical) etc My advice is don't .....

Don't play The Tennison Gambit... Don't Play the ICBM ... Don't Play The Englund Gambit, Don't play the BDG (I cited these because I see people plat the BDG, The Tennison (or it's close relative, the ICBM) as White... then roll with the Englund Gambit.)

At the beginner levels, your opponent's fall for the traps these are known for. As you move up in skill/elo the traps don't work.... Yet.... at this point if your play Bullet and Blitz time controls, your still winning because "through repetition" you've learned how to skirt around the bad positions and play the clock game. HOWEVER..... All this eventually comes to a grinding halt! The "How well you learn to skirt around the bad position " & "How well you learned to play aggressive risky chess while playing the "clock game" doesn't work when you start playing skilled players adept enough to pick apart the bad position(s) you stuck in.

All the above... comes much faster in slower time controls!! "where small tactical and strategic nuance" are seen and exploited in greater detail. In rapid and classical time controls by the late opening phase you are usually going to be stuck in a bad position or at best.... an equal position where the color you are playing has no advantage whatsoever... There you will spend most of your games fighting for equality... winning only if your opponent makes a ?? huge blunder. Again.... As you move up the elo ranks... that ?? huge blunder goes from dropping a piece to misjudging a strategic pawn maneuver in and endgame... Stuck playing a bad position where your a pawn down or behind in development (or maybe both) Your opponent's are going to attack those weakness each and every game... and still be able to to make mistakes and win the game... where you will not..

Play them if all you plan to do is play internet chess in blitz and bullet time controls... they will work for a while...