This post is part of our Money Face-Offs feature. Let us know who you think comes out ahead in this head-to-head match-up, and check out our other Money Face-Off posts.

In this corner, hailing from Beverly Hills and Las Vegas, is 91-year old billionaire investor Kirk Kerkorian, one-time amateur boxer know as "Rifle Right Kerkorian." And in the other corner, hailing from New York, is 71-year-old corporate raider and activist private equity investor, Carl Icahn, who is never afraid to go toe to toe with an opponent.

Let's get ready to rumble.

Round One begins: Kerkorian drops out of school and becomes a pilot. He gets his start in business buying surplus planes after World War II, as well as Las Vegas properties, becoming the landlord of Caesar's Palace. Icahn, meanwhile, establishes his reputation as a corporate raider during his hostile takeover of TWA in 1985, and becomes one of the inspirations for the character of Gordon "Greed Is Good" Gekko, the antagonist of the 1987 film Wall Street.

The last three decades have oscillated between private equity and venture capital. Right now, VCs are down and private equity is up. But 'clean tech' -- technologies that save energy and otherwise allow for a cleaner, greener world -- could revive VCs in the next decade while private equity licks its wounds.

In the 1980s, private equity was king. LBO firms were able to borrow huge amounts from banks and the junk bond market to finance hostile takeovers. The LBO boom ended badly with the collapse of junk bond king Drexel Burnham and overreaching in the form of the bidding war for the largest LBO in history --- RJR Nabisco.

In the 1990s, private equity imploded and watched with envy as venture capital prospered. It wasn't until the middle of the decade that VC firms like Kleiner Perkins were able to prosper from their investments in the Internet – beginning with the 1995 IPO of Netscape. The dot-com boom ended badly in 2000 with NASDAQ plunging -- it's down 54% from its March 2000 peak of 5,038 to its current 2,327.