Mick McCarthy's side defied the odds to stay up in their first campaign back in the top flight after a six year absence.
But they were aided by Portsmouth's financial problems and Burnley's dramatic slump in fortunes which meant only one place was effectively at stake in the final part of the season.
This time no team has been cut adrift with everyone still in contention to climb out of trouble with two games remaining.
Henry said: "It will be a bigger achievement to stay up this year. The league is more difficult this season. Newcastle and West Brom are certainly stronger teams than Burnley and Portsmouth - no disrespect to them - and also Blackpool as well.
"They are strong teams that have come up. Blackpool have surprised everyone, West Brom have done really well, Newcastle are really flying. It's a stronger league, no doubt about it so it's a way better achievement if we can do the job this year."
Source: PA
Source: PA