DBA says to do this but does not tell me why!!

This is my present table:

CREATE TABLE IF NOT EXISTS `geocode_us` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `loc_b` varchar(32) DEFAULT NULL,

  `loc_a` varchar(32) DEFAULT NULL,

  `lat` varchar(16) DEFAULT NULL,

  `lng` varchar(16) DEFAULT NULL,

  PRIMARY KEY (`id`),

  UNIQUE KEY `idx_name` (`loc_a`,`loc_b`,`lat`,`lng`),

  UNIQUE KEY `idx_name2` (`loc_a`,`loc_b`),

  UNIQUE KEY `idx_name3` (`lat`,`lng`)

) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=81814 ;

Code (markup):

He says to do this:
Recommendations:

Change lng and lat to DECIMAL(11, 8) or the desired precision.

If not required, remove the UNIQUE KEY idx_name, idx_name2, idx_name3

He did not say why or what this will do by changing this?



Also this:

This is my table:

CREATE TABLE IF NOT EXISTS `reviews` (

  `rating_id` int(11) NOT NULL AUTO_INCREMENT COMMENT 'The id of the rating',

  `rating_vendor_id` int(11) NOT NULL COMMENT 'The id of the page to be rated',

  `rating_user_id` int(11) NOT NULL COMMENT 'If a user is signed in, get their id',

  `rating` int(11) NOT NULL COMMENT 'The rating for the page',

  `rating_comment` longtext NOT NULL COMMENT 'The title of the page to be rated',

  `review_time` varchar(60) DEFAULT NULL,

  `review_title` varchar(124) DEFAULT NULL,

  `used_vendor` int(5) DEFAULT NULL,

  `reply` longtext,

  PRIMARY KEY (`rating_id`)

) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ;

Code (markup):

He suggest this:
Recommendations:

Change to InnoDB

Should change rating_id to 'id', just for programming standard

Add index on rating_user_id

ALTER TABLE reviews ENGINE=InnoDB;

CREATE INDEX by_user ON rating_user_id(rating_user_id);



Why should I do this and what will it do or improve?

Can anyone chime in on this?