static or dynamic wont matter regarding reliability of your line, ip lang yun( unless may routing issues yung subnet mo, which is minsan nangyayari talaga). kung naka dsl or non leased line connection ka, mas preferred ang dynamic lalo na kung wala kang need for vpn connections. mas secured kasi kung naka dynamic ka lalo na kung wala kang firewall, prone to ddos and backdoor attacks kasi. most, if not all, lease line connections static IP talaga ang binibigay.