From ThinkProgress - here's three of the eight:
1. Bush passed a huge tax cut plan, mostly benefiting the wealthy. Romney’s tax cut plan is four times larger, more heavily weighted to benefit ultra wealthy.
GEORGE W. BUSH: Passed $2.5 trillion in tax cuts over 10 years, 12.5% benefiting the top 1/10 of 1%. [ThinkProgress, 2/22/12; David Cay Johnston. 3/1/12]
MITT ROMNEY: Proposing $10.7 trillion in tax cuts over 10 years, 33% benefiting the top 1/10 of 1%. [ThinkProgress, 2/22/12; David Cay Johnston. 3/1/12]
2. Bush signed the McCain-Feingold campaign finance law. Romney supports repealing virtually all campaign finance laws.
GEORGE W. BUSH: Signed into law the landmark McCain–Feingold campaign finance reform, which put restrictions on “soft money” and limitations on spending from outside groups. [White House, 03/27/02]
MITT ROMNEY: Strongly defended the Supreme Court’s Citizens United decision, which overturned key provisions McCain–Feingold. Supports repealing virtually all campaign finance laws. [Mitt Romney, 2/18/10; ThinkProgress, 12/21/11]
3. Bush supported comprehesive immigration reform, a path to citizenship for 12 million undocumented immigrants and provisions of the DREAM Act. Romney opposes all of it.
GEORGE W. BUSH: Supported comprehensive immigration reform, including a path to citizenship for 12 million undocumented immigrants and provisions of the DREAM Act. [Reuters, 6/29/07; White House, 10/24/07]
MITT ROMNEY: Opposes comprehensive immigration reform and opposes providing a path to citizenship to undocumented immigrants and the DREAM Act. [Fox News, 04/03/12; ABC, 12/31/12]