The Liberal plan is marginally better than the Conservative plan, but it is still nowhere near good enough. A hybrid of both the Conservative and Liberal plans would be best. The largest provinces should gain seats from the smallest provinces and because of the limitations placed on us by the constitution, they should should gain more on top of that
That said, politically the Liberal plan is stupid. If the Liberals believe that the public is going to get behind their plan in order to save a paltry 15 million dollars they are delusional. There is no political upside to the Liberal plan and potentially a lot of downside. Not only will it not ingratiate themselves to those provinces who would loose seats under such a plan, such a position could easily be construed as self serving --- which it no doubt is. The Liberals do not want to see the number of seats increase because they feel it will make it that more difficult for them to win government. The we can not afford it fig leaf does not obscure this fact.
Anyway, given the Conservatives have a majority and will proceed with this no matter what the Liberals say, the Liberals need to do four things.
1) In order to make political hay, the Liberals have to develop a coherent approach to the issue of representation. That means hammering at the inequities of the system. Cities are underrepresented and hinterlands grossly over represented. The largest provinces are grossly underrepresented and the provinces with the smallest populations overrepresented. An empowered senate is incompatible with the notion of representation by population.
2) They need to diminish the political value of giving that many extra seats to Ontario, BC and Alberta by saying that the government did not go far enough and that Conservative government's push for an "effective" senate would make any such gains mute. Making the House more representative means nothing if the Conservatives plan to empower a second House that is not representative at all.
3) Forget about Quebec's wining; the Conservatives won a majority without Quebec this last time and with 27 seats being added outside Quebec its value will be even less next time around. "Western" Canada is little more than firm opposition to special treatment of Quebec by those living west of Manitoba. It is pretty much the sole thread that unites west coast hippies with Calgary oil men. If the Liberals have not recognized this after 40 years they deserve to collapse as political identity. Never ever ever mention Quebec's "special situation".
4) As Canada's third party, the Liberals do not need to be bounded by what is politically possible. In this case the Liberals should be calling for even more to be done to make the HOC more representative and the senate abolished to pay for it.